Demihuman

Demihumans are the Fantasy counterpart to Rubber Forehead Aliens. Related to Half Human Hybrids, Human Aliens, and probably others. Depending on the story, they've been called elves, dwarves, hobbits, orcs, trolls and many other names. The Five Races is a trope that classifies these creatures and explains how they live together in a setting that contains four or five such races; see that article for details.

Typically, creatures that fit this trope are fantastical beings which, despite being fantastical, are identical to humans in every way, except that they have:
 * a combination of stature and body shape which is just far enough from human norms that it would be clearly odd or unusual without being obviously nonhuman.
 * some physical feature (or more than one) that is slightly yet obviously outside human norms, such as Unusual Ears or Cute Little Fangs, and instantly identifies them as nonhuman to any racist or Dangerously Genre Savvy human character. Often this feature is easily hidden by clothing that is easily lost.
 * some sort of affinity for, or resistance to, Functional Magic.
 * a nonstandard lifespan.

They may also:
 * have a combination of skin, hair, and eye color that is outside the range for humans.
 * be Always Chaotic Evil, Always Lawful Good, etc.
 * possess abilities/senses well beyond (and/or skills far superior to) the human norm.

Anime

 * In Record of Lodoss War, elves, dark elves, dwarves, and grassrunners. Goblins, ogres, and kobolds are treated as barely-human monsters.

Fan Works

 * C'hou in With Strings Attached has elves, but Word of God states that they're just another race of humans with pointy ears and fine features. However, the Hunter's world has goblins and trolls.

Literature

 * JRR Tolkien (The Lord of the Rings, etc): Elves, Hobbits, and Dwarves, and maybe orcs/goblins and trolls depending on your interpretation.
 * There's some grounds for supposing that Hobbits are a sort of pygmy human. Tolkien went into some details about the origins of the other humanoid species, but never mentioned anything about the Hobbits.
 * Adaptations of Tolkien's races and their Theme Park Versions appear in many, many, fantasy novels since, sometimes filtered through Dungeons and Dragons.
 * Discworld: dwarves, gnomes, vampires, werewolves. Trolls are about as normal as people; they're just biologically very distinct--demihuman in treatment, but not in biology. Elves are Always Chaotic Evil.  appear in Unseen Academicals,.
 * The Marat in Codex Alera. They look human, but they all have white hair, Bond Creatures, and some other things that set them apart from humans. Justified, as they are implied to be descendants of Neanderthals who were brought to Another Dimension.

Tabletop RPG

 * Dungeons and Dragons: elves, dwarves, halflings, gnomes (in 2e), irda (in Dragonlance) teiflings and eladrin (in 4e), etc.
 * The trope-namer; 1st and second edition D&D used the term "demi-human" to describe the "good" races and "humanoid" to describe the "evil" races of orcs, goblins, bugbears, etc.
 * And Planescape did away with this trope entirely, explaining what the prefix "demi-" actually means. For example, demigod doesn't mean "like a god" it means "half god".
 * Parodied in Toon: in the "ToonQuest" setting the equivalent to humans were Dogs, dwarves became Badgers, elves turned into Squirrels, and halflings became Mice. The capitalization is where the 'demi' part comes in -- yes, these races are specifically distinct from regular old Toon dogs, badgers, squirrels, or mice as dictated by the rules of the mighty wizard Teeyessarr.
 * Shadowrun has "metahumans", but the concept is pretty much the same. Mainly, there are elves, dwarves, orks, and trolls, but some of the other races show up in The Shadowrun Companion as subraces of those.
 * The Marvel Super Heroes RPG used the term "demihuman", but it referred to Petting Zoo People, despite being made by the same company as D&D, TSR.
 * In New Horizon, not only are there three races of Ridiculously-Human Robots, but there's also the group of humans who merge with wild animals called Medeans.
 * Warhammer 40000 started as a straight analogue of Warhammer Fantasy Battle IN SPAAAAACE but evolved over time with some additions and some removals. So far there have been Squats (Dwarfs), Eldar (High Elves), Dark Eldar (Dark Elves), Exodites (Wood Elves), Ratlings (Halflings), Ogryn (Ogres), Orks (Orcs) and Space Undead (Undead) (the latter started off literally as skeletons in space but have now become the Necron legions).

Video Games

 * The Elder Scrolls has elves in pretty much every flavor, as well as orcs and dwarves, which are just different flavors of elves in that continuity.
 * Chrono Cross
 * Elemental War of Magic - The only "official" one is the Fallen, a bunch of half-dragon, half-human gents.
 * Angels and humanoid Demons in Disgaea.

Web Comics

 * Twice Blessed: elves, dwarves, gnomes, goblins, hobgoblins, orcs, ogres, etc. Like OotS below, it's based on Dungeons and Dragons.
 * The Order of the Stick: Again, elves, dwarves, halflings, goblins, hobgoblins, orcs, ogres. Fitting, as it's based on Dungeons and Dragons.
 * Drowtales: see here.
 * Linburger has the Cyll, the Trokks, Firne, and Mirrakae. All of which suffer Fantastic Racism, and most live in poverty in the slums. Though there are a few rich demihumans, such as a pornstar.
 * Speak With Monsters mocks the human-centric nature of this trope with a list of alternate names for humans, ranging from "double halflings" to "I can't believe it's not bugbear."
 * El Goonish Shive has elves, who are offspring of Immortals and humans, and Greater Chimera, who are offspring of humans and a species of aliens called Uryuoms through the aliens' Bizarre Alien Reproduction. Greater Chimera can have animals among their genetic parents but if they don't they are visually identical to humans except for their very unusual eyes and the fact that they have at least a pair of furry antennae on their heads.

Web Original
"King: No, no, NO! I said slay the dragon, not lay the dragon!"
 * The art of Fredrik KT Andersson (Not Safe for Work!): elves, dwarves, gnomes, orcs (who look like cavemen with tusks), trolls (who look like a human with a lion's tail). Not to mention tons of Half Human Hybrids, many of them the result of a certain bard who gives new meaning to Anything That Moves:

Western Animation

 * Fairly Oddparents has fairies, genies, pixies, anti-fairies and lawn gnomes.
 * Fairies are have insect wings and are the size of children. Interestingly, their eyes match their hair.
 * Genies are about the size of humans, and have tails of smoke. They fly, despite not having wings.
 * Pixies are like fairies but evil, and all sound like Ben Stein.

Real Life

 * Neanderthals, a physically hardier species of hominid (or possibly sub-species - it seems they weren't as different to us as was thought at first and inter-breeding may have been possible).