Okay, here we go. This list should be significantly shorter than dwarves and elves, of course. Once again, feel free to correct me if I've left anything out or if you find any mistakes.
- Cerillian Gnome: Probably not much different from standard Rock Gnomes (MM). Extinct since the Battle of Mount Deismaar.
- Athasian Gnome: Also extinct, wiped out by 'humanists' a few thousand years ago or something.
- Gnomoi: aka Thinker Gnomes. The gnomes of Krynn's northern continent, well known for their fantastical technological achievements. Identical in appearance to Rock Gnomes. Called 'Mad Gnomes' by Minoi because all their inventions work - a clear sign, to the Minoi mind, that they're a little off in the head. Sometimes born to Minoi parents.
- Minoi: aka Tinker Gnomes. The gnomes of Krynn's southern continent. Actually descended from humans who were cursed to tinker endlessly as gnomes by the god Reorx. Also identical in looks to Rock Gnomes. Technologically adept, but not very wise - they have hundreds of different ways to say 'Look out!' None of their inventions work, and for some reason they see that as a blessing.
- Forest Gnome (MM)
- Svirfneblin: aka Deep Gnome (MM)
- Rock Gnome (MM)
- Zakharan Gnome: Similar in appearance to Rock Gnomes. Like all nonhumans in Zakhara (even orcs and ogres), they are fully integrated into society.
- There are no gnomes native to Kara-Tur or Maztica.
- Rock Gnome (MM): Found scattered throughout the Known World.
- Sky Gnome: Once again, these look just like Rock Gnomes; it's their culture that sets them apart. Found only on the floating isle of Serraine. Commonly found piloting primitive aeroplanes. From 'Top Ballista'.
- I'm not that up on Mystara, so if I missed anything please point it out.
- Nidavellir Gnome: The gnomes of Ysgard, magically adept, found fighting for space with the dwarves and good drow.
- Planar Gnome: Any gnome born on the planes.
- Ravenloft Gnome: See Ravenloft 3E.
- Wildspace Gnome: Interestingly, gnome ships in Wildspace usually have three different subraces on board: Gnomoi from Krynn to pilot the ship, Minoi to keep it going (look out!), and Rock Gnome illusionists to power the ship. Of course, the illusionist is unnecessary if they've got some Giant Space Hamsters in treadmills to power it instead.
World of Greyhawk:
- Forest Gnome (MM)
- Rock Gnome (MM)
- Svirfneblin (MM)
Gnomes from no particular campaign setting:
- Arcane Gnome: Wizardly gnomes who like to buy up parts of human cities for their own habitation. From Dragon 291.
- Barbaric Gnome: 'Hero Builder's Guidebook' suggests a savage subrace of gnomes that might produce gnome barbarian PCs.
- River Gnome: Xenophobic swimmers who just want to be left alone. From Dragon 291.
- Spriggan: Evil fey created in mockery of gnomes by either the Queen of Air and Darkness or Urdlen, depending on who you ask. See 'Fiend Folio'.
- Uldra: Not really a gnome, but bears mentioning. Close relative of gnomes and dwarves found in arctic tundras. Friendly with animals. From Dragon, now in the Creature Catalog.
- Jermlaine: aka Banemidges or Jinxkin. Officially (in MM2), these nasty little buggers are fey, but an article in Dragon Magazine suggests that they were actually created on the World of Greyhawk as a servant race by a cult of evil gnomes by combining human and gnome features into a much smaller creature.
- 'Dwarves Deep' mentions that dwarves and gnomes can interbreed.
- The 3E DMG suggests half-gnome/half-halflings as an idea for a PC race.
- I think gnomes can also breed with kender, maybe elves as well?
Man, this is going great. So far we've chronicled elves, dwarves, and gnomes in this manner and I think it's going to pay-off.
I noticed there was no "Gnomes from Earth's Dark Ages" in this one, but that's probably because gnomes are... well, not all that popular in mythology. They're just gnomes, I suppose. Not very many types in real world cryptozoology.