Fan Verse

When fanfiction writers do several (not just a few, several) fics for the same fandom in the same continuity as each other, that's a Fan Verse. World Building counts a lot toward this label, as well.

If they keep it coherent and get enough interest, Fan Verse writers can single-handedly influence Fanon, possibly to the point of being canonized as an Expanded Universe.

If several authors all contribute to a single Fan Verse, it becomes a Shared Universe.

Anime and Manga

 * Legacy of the Rasengan by Tellemicus Sundance has spawned its own fan verse in recent years, especially now since he has given up on Chuuten and has chosen a successor to continue it.
 * The Sailor Moon Expanded community was a prime example of a Fan Verse. The writings of over a dozen authors were combined with the goal of adding new and interesting characters, stories, and information to the Sailor Moon universe without contradicting established canon. In many instances, particularly in the works of Mark Latus, the expanded material is more interesting and concise than the original source. It hasn't been updated with new material in quite some time, however.
 * Richard Lawson created two such Fan Verses for Ranma ½ during the late 1990s:
 * Thy Inward Love is a Continuation fic that picks up at the end of the Ranma manga and attempts to resolve the series' Love Dodecahedron and corresponding web of honor entanglements; in addition to the main storyline there are several prequels and side stories, and a sequel series.
 * Thy Outward Part is an Alternate Universe Fic where Ranma is locked in female form permanently in the wake of a different, more tragic outcome to the Chisuiton arc of the manga. Pushed away by a homophobic Akane, Ranma goes to college alone and unhappy, until she meets a young man who finds her attractive and wants to learn martial arts from her. Long thought to be "closed", this 'verse was revived in the early 2010s when Lawson started writing stories in it again.
 * Lawson has also written a series of five All Purpose Cultural Cat Girl Nuku Nuku fics that describe the remarkable life and evolution of the ostensibly comedic title character.
 * There is a Digimon fanfic series that goes like this: The first two season are one continuity, while the third, fourth and fifth all get their own, outside of the elements of Ryo and his OC Ben (an American Chosen/Tamer) which serve as continuity links between the Adventure and Tamers worlds. They have been on a long hiatus, and there may not be any more.
 * There is a truly awesome one of these for Urusei Yatsura called The Senior Year, started by Fred Herriot. It takes the original setting, characters and runs with them, adding new and interesting characters, places, cultures (including many ShoutOuts to other anime) and spans at least 20 years through its various sequels.
 * The Neon Genesis: Goddess series by Slayer combines Neon Genesis Evangelion and Ah! My Goddess for an interesting effect on the story of NGE. It also has about two dozen spinoffs and continuations.
 * "Superwomen of Eva" turns basically the entire female cast of Neon Genesis Evangelion into superheroines. Misato becomes She-Hulk, Asuka Ghost Rider, Rei the Silver Surfer, Ritsuko Spider-Woman, Maya all the Fantastic Four, Mana Iron Man...even some spinoff-only girls and the canonically dead mothers get into the game.
 * Neon Genesis Evangelion: R was all written by one author but it has two branching continuities and has itself spawned fan fiction (such as Neon Genesis Evangelion: R: Redemption). It's also unusually detailed for a piece of fan fiction and elaborates substantially on the nature of the angels compared with the original series.
 * Megatokyo has spawned at least three Fan Verses to date. The oldest is the Megatokyo: the Clans game that started in 2001 on the Megatokyo Forum, and which is still going (look for threads labled [Mt:tC] in the RP subforum). More recently is the Story Discussion Fanworks game that is hosted off site in its own dedicated forum. Most recently is the energetic Megatokyo Campfire Story that can be found in the fanart subforum.
 * In Naruto fandom, the Lace and Strawberries or Saki-chan Fan Verse, started by Asuka Kureru or Askerian. The basic premise is Sasuke dealing with his issues via cross-dressing as a Gothic Lolita that goes by the name of Saki. Not actually crack. While she has written only three fics in this verse, the number of fan-fan works has possibly reached triple digits, and includes writers such as chibirisu-chan, ice-dark elf, and crazy-toffee.
 * The Continuance of Haruhi Suzumiya by Hejin57. This series branches directly off the anime adaptation of The Melancholy of Haruhi Suzumiya. Starting with The Attraction of Haruhi Suzumiya, this story has already seen three completed sequels, and another already in the works. Set for six stories in total, this fanfic series easily qualifies as a Fan Verse. All the stories in the series are great, too!
 * One Piece has one in the Crew of the Axe Universe due to the main fanfic crossing over with several other fics, and those fics crossing over with more fics.
 * Ashamed as I am to bring this up, I can hardly believe it hasn't been here yet. It's very much a fetish fanfic crossover, but it's been around for a long time and spawned many storylines, including multiple interactive "Choose Your Own Adventure" style stories. It's the very NSFW fanverse Wild Horses And Pokegirls where Ranma is sent to a very twisted Pokemon altverse where, at some point in history, women were crossed with pokemon so that now, everyone has some level of poke DNA, and very few girls look human, especially after puberty. Those that do, don't usually stay that way for long.
 * Debbie (Dai-chan) began The Powers of Crests universe for the Digimon fandom on Fanfiction.net, which was expanded upon by Creedogmon, and an author named DayDreamer9 has begun a third imagining.
 * Arceus Archives, otherwise known as the Archiverse, is one of these to the Pokémon fandom.

Comic Books

 * The Private Diary of Elizabeth Quatermain is an LXG fic series which picks up where the movie left off. The OC narrator is Quatermain's perfectly ordinary, un-powered daughter, who ended up living with the League when  caused her to lose her home and her place in London society. It took four years to write and stretched across five complete multi-chapter stories, plus a handful of side scenes and alternate points of view. The final installment crossed over with the same author's unfinished Sherlock Holmes fanfic, thus indicating that the two stories take place in the same continuity. Additionally, a few other people on Fan Fiction.net actually wrote fanfic about the LXG fanfic, a phenomenon which perhaps merits its own trope.
 * Batman has an epic series known as the Cat Tales universe which some people think of as better than some of the published stuff. It has lots of awesomeness for many characters, but the main thread is attempting to create a realistic romance between Batman and Catwoman without sacrificing any of their characters' awesomeness. This is mixed in with liberal amounts of drama, humor, believable character development, and tons of great action. The first story is A Girl's Gotta Protect Her Reputation. And best of all, the author is still going strong after more than 70 stories and nearly twenty years—the first chapter of the first story was published on March 8, 2001. With regular updates every few weeks, no less!
 * Also has a fair number if sidestories in the same verse co-authored by others, fan-art and its own website, here
 * There is a fanfic version of the Marvel Universe that puts much more of an emphasis on lesser-known heroes and villains, such as the 1990s superhero Sleepwalker, rather than mainstays such as Spider-Man, the Fantastic Four or Captain America (comics), who usually guest star in the C-listers' own stories rather than get the main spotlight. Many aspects are also heavily reimagined, such as Gwen Stacy being alive and well as Peter Parker's one true love, and Mary Jane Watson developing her own spider-powers as Spider-Woman, with her own rogues gallery and supporting cast entirely separate from Peter's.
 * There are several fanfics written by the same author using DC Comics heroes set during the 1940s mixing elements of modern continuity with Golden Age tropes. Word of God says the basic impetus of this retro-style Fan Verse was an excuse to write a story where Superman actually gets to punch out Hitler.
 * On LiveJournal, the DC Universe RP of JLA Watchtower and its spinoff DC Nation has been going strong since 2004, using a combination of adapted DC Comics storylines and original plots. There have also been "flashback" posts that go into earlier parts of DC continuity.
 * The best-known Watchmen fanverse is a magnificent Zombie AU, of all things.
 * The Shadowchasers fanverse, started by the Fan Fiction great Black Panther, has spawned several continuing fanfics on fanfiction.net.

Literature

 * The DAYDverse, a darker take on Harry Potter started by Thanfiction and expanded upon, with the primary protagonist being Neville Longbottom. Starts with a parallel story to HarryPotter and the Deathly Hallows and continues with the second of three books called "Sluagh," as well as numerous one-shots, missing scenes, and character profiles.
 * On the subject of Harry Potter fic, the Dangerverse arguably qualifies as a Fan Verse. Started by whydoyouneedtoknow (and yes, that is a The Incredibles reference), the story reimagines the canon entirely. At last count the mainline story was at 1.18 million words and counting. As with the Dumbledore's Armyverse, there are numerous one-shots, missing scenes, and numerous Alternate Universe fics by the author. At last count there were at least four alternate universes written by other authors.
 * Author bedlamsbard on LJ has at the very least two—no, wait, working on three Narniaverses—Warsverse, Petaverse, and now possibly Casverse. Also Dustverse, which is really a continuation of Warsverse. I think. And every single one of them is freakishly amazingly written. Particularly Dustverse.

Live Action TV

 * At its height, Power Rangers had loads of these, including "Personality Conflicts" by Ellen Brand and "Earth Crystals" by Jeremy Ray Logsden. Sadly, neither of these have been updated in years.
 * Ellen Brand's Danny Phantom fics and her Detective Conan "Unprofessional Opinion" series are actually set in the Personality Conflicts Expanded Universe.
 * Dead Fic averted! Eleven years passed between Allied Powers and Hide and Seek, but Personality Conflicts is being updated again.
 * Star Traks - This is a parody Fan Verse for Star Trek, covering TOS, TNG, and DS9. Also has an X-Files variant called Traks Files.
 * Ambassadors of Liberty is a Stargate RP site with several other settings in the pipelines.
 * LiveJournal author miggy has provided Glee with the Mostverse, a small but growing set of Continuation stories mostly centered around Rachel and Kurt going to college in the Big Applesauce and rooming together. It's remarkably in-character, not to mention Original Flavor.
 * All of the Doctor Who stories on Richs Comix Blog (possibly with the exception of Landry Walker's "Seeds of Destruction") are built around the same continuity as the blog's best-known fic The 10 Doctors. This universe excludes the Doctor Who Expanded Universe; and thanks to Crossovers, it also includes Forever Knight and Jem.

Tabletop Games

 * The now-defunct Global Guardians PBEM Universe was the largest Shared World Champions Fan Verse on the net.
 * Warhammer 40,000 fics often include references to Love Can Bloom and its sequel(s) with Lofn (half-Eldar child of that pair, if only for Crack Fic potential of someone with natural psychic field pacifying even lesser Tyranids to the point where she may treat them as Ugly Cute pets). The later Dawn of War canon (that is,, but only a few years later) may or may not be included.

Video Games

 * Freedom City Play By Post is the largest online source for stories in the Freedom City setting. Characters use the Mutants and Masterminds rules set to make things a little more balanced than the usual collaborative free-form stories.
 * Fritz Fraundorf's Massive Multiplayer Crossover comedy writings, borrowing from every Role-Playing Game he's ever played.
 * Eric "Erico" Lawson's Legacy of Metal consists of over a million words of Mega Man and Mega Man X fanfic spanning nearly two centuries of history (2039-2222). Much of it expands on the plot points of Rockman the Robot War in Broad Strokes as well. The author has posted a timeline and retrospective descriptions of each fic (scroll down).
 * All of the works within the Warcraft fandom by Weiila take place in the same universe.
 * Xanrivash on fanfiction has created a fanverse for Kingdom Hearts that gives the Organization members larger backstories and fleshed-out personalities.
 * Thanks to the fact that the canon characters are largely skeleton characters made of tropes specifically to give the fan fic writers more latitude, Touhou largely relies upon a collective subconscious understanding of what each character is, with each fan fic author slighly altering the character more in line with their own tastes (such as a violently self-centered Reimu to a just plain ambivalent Reimu), but relying upon the same tacitly agreed-upon traits. A few have proper names and are based on popular or highly-exposed fanwork; these include Walfas's math-joke-heavy Flash cartoons and the action/parody Advent Cirno. There is a minor, infamous (at least on Pooshlmer) 'verse called the 'Soak.
 * One author has written several Mass Effect stories set in the same 'verse with her primary/main Commander Shepard. And since we're on the subject in general, it's fairly common for some ME fan fiction writers to have their own 'verses as well. It is expected that this will become a lot more common when Mass Effect 2 is out.
 * Not to mention the Cerberus Daily News forum where fan characters interact and RP with each other whilst still existing in the confines of the canon.
 * Static Space is a fanfic-verse derived from Asteroids of all series, inspired from Luke Rounda's (in)famous story, Asteroids: Festival Among the Rocks.
 * As the game Oolite is itself a Fan Remake of the classic Elite, its Expanded Universe is basically a Fan Verse for that game by proxy.

Web Comics

 * There are several fanfics by the same author with Terinu set in the period prior to the canon storyline, set just after the Varn Dominion's conquest of the Earth, one set in Vulpine Prime's past just prior to their conquest by the Dominion, and a notable crossover with the Season Five Stargate SG-1 team. At least a couple of fanfics by other authors have crossed over OC's, and a couple of bits of Fanon were incorporated into the main storyline by author Peta Hewitt.
 * The Homestuck fandom has a few. For instance, there's the TROLL!COPS AU, which puts the characters in a Cop Show-like modern setting. Or the Population series—where the twelve trolls settle down on Earth after the canon plot is over. The stories tell about how the trolls and their numerous progeny try to integrate themselves into Earth society, have wacky interpersonal hijinx, and lots and lots of sex.
 * Inonibird's MGS3 universe from The Cobra Days became so popular that other fans started writing in the same universe. Some notable fics to come out of it include "Strange Wind" and Ryuichifox's art and writings about the Fear and the Fury.

Web Original

 * The Whateley Universe, being a web-based fiction universe, makes this easier. On the website, there is a place for Fanfic, and there are like 20 different authors writing additions to the Whateley world, most of the taking place (sooner or later) at Super-Hero School Whateley Academy.
 * That Guy With The Glasses fandom tends to be, strangely, a breeding ground for this (and they're mostly Dark Fic for some reason). There's That Guy with the Glasses in Space, Escargoancitizen and Friends, a verse where Linkara is a Vampire Hunter, a Victorian AU, a Hooker!Verse, a verse for their genderswapped doubles, a Hypno!Verse where Insano has brainwashed everyone and an AU where Linkara has snapped because of a creepy obsession with Spoony.
 * Cumberholmes is a fanverse based on a group of roleplayers on Twitter, and their interpretation of the characters.
 * In general, all of the fanfiction written for a particular genre by Michael2 takes place in the same Fan Verse, e.g., all of the Sliders fanfiction written by Michael2 is in the same Fan Verse.
 * Fan Author Allronix usually keeps a single continuity per fandom, meaning most of her stories for a given universe will tie together.

Western Animation

 * Anthony Bault took up the reins of a rather well-known Fan Verse (at least well-known in his corner of the Internet) called Arcadia. It's loosely based off the "Captain N: The Game Master" theory, that all the game universes (Sonic The Hedgehog, Super Mario, Legend of Zelda, he's even crammed in every single anime he's ever watched into an "Ani-Earth") are connected. His work can be found here.
 * Ani-Earth is a completely different story altogether - it was a series of stories by another author that started out as a simple crossover between Sonic the Hedgehog and Tenchi Muyo! and spiraled out of control there!
 * The Sanza Salazar trilogy, a series of Teen Titans fics branching off from the end of season four which explore the identity of the thief Red X, whose identity went unrevealed in the original series. The second fic of the trilogy is a Fix Fic, while the third re-envisions the fifth season that the trilogy itself disregards.
 * The Sanza Salazar series is now getting a fourth installment taking place shortly after the third and written by an entirely different author than the original trilogy.
 * The so-called LegendVerse, also in the Teen Titans fandom, has existed since the end of the first season and has been added to by more than half a dozen writers, though only the originator consistently contributes to it at this point.
 * Daria fanfic has expanded outwards into what's actually known as the ' Daria Expanded Universe ', with such fandom-created characters as Lynn Cullen, Jim Vitale, Richard Rawlings, Michael Fulton, Alfred Phelps and Col. Kyle Armalin freely interacting with the canon characters. (Daria fans know these folks as if they had been on the show itself.) On the fandom's Wiki, there's actually a listing for the ' Daria Multiverse '.
 * An impressive collaborative series was written for the Gargoyles series. What was notable about this was it based its story arcs on Word of God information about the future of the cartoon series, had it not been canceled. It included three "seasons" for the main Gargoyles stories, but also branched out with Brooklyn's time travel stories, the adventures of King Arthur and the London clan, and the story of the Scotland clan before its destruction.
 * The Arthur Goes Fourth fan-verse. Yes, an Arthur fanverse. It has two spin-offs, each set in a different grade.
 * Transformers Animated has three prominent authors who influence each other and built their own FanVerses by bouncing off their ideas. There are a ton of minor universes they write about, and they seem to have a blatant disregard for canon, so avoid if that doesn't work for you.
 * The Chip 'n Dale Rescue Rangers fandom has a couple of its own, started as a continuous series of Fanfic and often picked up by other authors than the original one. The first one was the series The Adventures Of Gadget Hackwrench which, after the success of the epic hallmark Rhyme And Reason, encouraged Rangerphiles to start writing and sort of launched the Ranger fandom's rich Fanfic tradition. The most famous example, however, is The Nowakverse. Others are, for instance, Chip Noir Dale's Rescue Rangers or The Midnightverse.

Unorganized examples

 * The "Fanfic Domain", created by fanfiction.net's Crazyeight, is both Fan Verse and metafictional masterpiece. One of its central premises is that authors are bodily transported to the Fanfic Domain and meet characters face-to-face; canon events actually happened to the characters and they actually experience the fanfics into which they are written. Enter Fan Dumb, and with it, plot.
 * In the early days of the Sonic the Hedgehog cartoons (specifically Sonic Sat AM), several Big Name Fans, such as Bookshire Draftwood and Dan Drazen, did this. In fact, they did it in such a way that their own verses could theoretically fit into each other's with little difficulty. These Fan Verses got so large and popular that dozens of other writers over the years contributed with episodic stories that could also slip right in, culminating in a pretty massive web with hundreds of connected stories.
 * Possibly the largest Fan Verse is Eyrie Productions, Unlimited's Undocumented Features, with going on 30 years of work and a coherent setting spanning at least 500 years of in-story time (and thousands of years of history), and incorporating literally hundreds of sources.
 * There is a whole fanfic universe, written by one author meshing every piece of fiction she knows into a whole multiverse. This is infact lampshaded in this part of the story: Firestar looked at the middle-aged twoleg in the brown hoodie. "Since when did the forest be so close to your "HQ" and "Riverdale"? Are you messing with my head, twoleg?" The twoleg replied "It's not my fault, it's GOD'S fault for mashing every piece of fiction together!" ...And to think her fanfics were pulled off of Fanfiction.net...
 * The Aethion Expanded Multiverse is a universe where any Bionicle fanfic writer can put their own work in and be considered "fanon" for the universe.
 * Immortality Protocol Cy-Fox is a fanfic-verse derived from Sonic the Hedgehog which takes place Exty Years From Now in what is perceived to be our reality (minus the obvious creation of the Sonic games in the 1990s)
 * The Fantendoverse is basically the definition of this.
 * The Teraverse started off as a blend of The Secret World of Alex Mack and the DC Universe, but once a dozen or more other authors got involved it became a setting that is shaping up to rival Undocumented Features for its scope and number of sources.