Spider People

A centaur-esque creature that has the upper body of a human and the lower body of a spider, sometimes referred to as Driders. Most of the time they are seen as females since female spiders are bigger and more dangerous than males (also serves as a form of Fetish Fuel). They're usually shown as evil beings but occasionally fall into the Cute Monster Girl category.

Not to be confused with Spider-Man or Spider-Woman. See also the Youkai Tsuchigumo and Jurogumo, which are spiders that can turn into people and often have mix-and-match shapes similar to this trope. Naturally, tend to have an Arachnid Appearance and Attire.

Mythology

 * In Greco-Roman mythology, there was a mortal weaver named Arachne. Arachne boasted of how her skills in making beautiful tapestries were better than those of Minerva, the Roman goddess of wisdom and crafts. Minerva grew so tired of her boasting that she turned Arachne into a spider woman, proving that Spider People are indeed Older Than Feudalism.
 * She was actually just turned into an ordinary spider, but modern adaptations will usually have her turned into either this or a Giant Spider.

Anime and Manga

 * Arukenimon's true form from Digimon Adventure 02.
 * Keito from Rosario+Vampire is the local Jurogumo.
 * Captain Talleran from One Piece is a literal Spider Monkey. As in, body and legs of a gigantic spider combined with the hands, head and tail of an equally big monkey.

Comic Books

 * Arachne appears in The Incredible Hercules as she battles (of all people) Spider-Man.
 * The Crimson King in the comic adapation of The Dark Tower.

Film -- Live Action

 * Not half-spider but definitely half-arachnid: The Scorpion King (at least in his appearance in The Mummy Returns).
 * The spidermonkey in Spy Kids 2 was half-spider, half-gorilla.

Literature

 * Tenebrites in Quest For The Fallen Star have this as one of their two forms (the other form is fully humanoid). They wear full plate in both states.
 * Spidrens from Tamora Pierce's Tortall Universe, which have a spider's body and a human head.

Live Action TV

 * A non-human example: The aliens in the new TNT series Falling Skies have spider-like bodies, but their heads and forearms are more like the creatures from Alien.
 * The Captain Proton holodeck episode from Star Trek Voyager featured Janeway as Aracnia, Queen of the Spider People. Presumably had we seen the spider people, this trope would have been involved.
 * There is the Queen of the Racnoss from the Doctor Who episode "The Runaway Bride", she even had a web motif going on for her spaceship. Full spider below but human upper torso and semi-human head (the actress wore a prosthesis with a big frill on it).
 * The Hercules: The Legendary Journeys episode "Web of Desire" showed a different take on the Arachne myth. She was jealous of her daughter's beauty and drowned her in the ocean. Zeus cursed her into a Spider Person form and banished her on an deserted island.

Tabletop Games

 * Dungeons and Dragons's Driders, who are transformed drows.
 * Lolth, queen of the spiders, I believe, was the prototype for the Driders.
 * Forgotten Realms has Choldriths, female forms of the multi-armed humanoids Chitines.
 * Tsabo Tavoc, the Phyrexian general from Magic the Gathering.
 * Sheoldred of the New Phyrexians have a similar look, although the lower portion is more like a cross between a spider and a crab, with four legs. And a giant mouth across its entire front,

Video Games

 * The Spider Witch boss from Ghostbusters the Video Game.
 * The Contessa from Sly Cooper 2. She's not really human but in a world where every character is an anthropomorphic animal she kind of stands out.
 * On variety of the Nerubians from World of Warcraft are like this, with spiderlike lower halves and humanoid upper halves. Although in fact they only have four legs. Most of them are insectoid or arachnoid throughout.
 * The Lesbian Spider Queens from Lesbian Spider Queens of Mars.
 * The Spider Queen, one of the bosses in Gauntlet: Dark Legacy, was drawn this way.
 * The Star Ocean games have this as a recurring enemy type. Specific enemies are named Arachmene, Black Widow, Scylla, etc.
 * Inverted for the Sharan, a race of spider people in the old Polish rpg Krysztaly Czasu - they are spiders from the waist up and look really awkward (even though their claws had enough dexterity to handle items)
 * Arachne is an enemy in the Castlevania series.
 * And a GINORMOUS one in Order of Ecclesia.
 * The Spider Daedra from Oblivion are half-woman, half-spider.
 * In Battlespire they're half-men, half-spider.
 * The Vagary from Doom 3, a demonic-spider-woman who appeared to be telepathic and telekinetic.
 * One of the bosses from the video game version of Flushed Away looks like this.
 * The Tarantula Mistresses from City of Heroes.
 * Drachnids in both Ever Quest games. Upper body of a Dark Elf, lower half of a spider. Made as an experiment / wedding gift by an especially crazy sorceress toward an exceptionally powerful vampire. He didn't care for them, so he released them on Kunark where they quickly populated.
 * Spider-Human hybrids were meant to be the next step up from the first Resident Evil's Chimera monsters, which were humanoid flies. Unfortunately, the concept was created during Resident Evil 2's 1.5 phase -famously abandoned during a late build by the creators, and the creature went along with it.
 * The dark elf unit Spider Queen, in Age of Wonders 2.
 * Two appear in Dark Souls. The first is a boss fight; Quelaag is half-naked-woman, half-MAGMA-spider, so you spend quite a lot of time dodging flame bursts and lava flows. The other is her unnamed sickly albino sister. "The White Lady" is friendly enough (because she's so ill she thinks you're her sister) and acts as a fire keeper.
 * The aptly-named Arachnos in Titan Quest have humanoid torso and spider body. Their queen Arachne is a giant boss monster. Later you can find the asiatic Arachnos, which are brightly colored and have the head of a tarantula, fangs and beady eyes included. Scorpion-people are met in Egypt, but they're not centaur-like.
 * Baal is this in Diablo.

Web Comics

 * Spinnerette has a bad turn when her Lolth-worshiping nemesis "Evil Spinnerette" uses ancient relics and a first-edition Dungeons and Dragons manual to turn herself into a drider. Later she even cons Spinnerette into helping her repeat the feat with two of her minions--complete with a Gender Bender for the male that includes a Lampshade Hanging about the advantages of being female when you turn into a spider.
 * Manspider is a very squicky NSFW Rule 34 webcomic built around this concept.

Web Original

 * Arachnes are in The Monster Girl Encyclopedia. (NSFW)
 * As are Jourugumo and Girtabilu (altough the latter are half-scorpion).
 * Living With Monster Girl has an Arachne as well. (also NSFW)
 * N'ktane from Tasakeru
 * The dridders from Felarya are a larger than usual (as in, really frickin' HUGE) example of this. (Will they eat you? Of course they'll eat you, this is Felarya.)

Western Animation

 * The title character of the Billy and Mandy episode "The Wrath of the Spider Queen", pictured above.
 * Veronica from American Dragon Jake Long.
 * Rosie from A Bugs Life actually looks like this, despite being an actual spider.
 * Also, one of the mutant toys from the first Toy Story film appears to be a baby doll's head mounted onto a spider body made from an Erector kit.
 * Mr. Waternoose from Monsters Inc..
 * Tarantulus and Blackarachnia from Transformers are basically roboticized versions of these.
 * And Airachnid (a Blackarachnia lookalike) from Transformers Prime.
 * Nephilia from the 1981 Spider-Man animated series, and Arachnoid from Spider Man and His Amazing Friends.
 * Baxter Stockman in one later episode of Teenage Mutant Ninja Turtles 2003, due to him losing his human body from the neck down.
 * Variation: One of the villains from The Secret Saturdays has a scorpion lower torso.
 * A robotic scorpion lower torso.
 * Darth Maul in the Season 4 finale of Star Wars the Clone Wars, similar to the Secret Saturdays example above. He does lose all but two robotic legs thanks to Mother Talzin's magic, however.