Vintage Gaming Network - Formerly Dave's Video Game Classics. This is the one that started it all (at least for me) and was the best in its day. Unfortunately, legal issues really screwed up this site. However, it is still an excellent source for emu news, emulators, MAME sounds, and more.
Retrogames - Your one stop emulation site - With up-to-date news, emulators, ROMs, and links, it is truly your one-stop site. In my opinion, the best site today. Includes ROMs for the most recent version of MAME.
Arcade@Home - Another excellent all-around emulation site with an up-to-date MAME ROM section.
Arcade ROM Heaven - Where all good roms are laid to rest. Also includes emulators and ROMs for the most recent version of the popular emulators.
Arcade ROMs from Japan - A large list of arcade ROMs, many of which are not currently emulated.
ClassicGaming.com - Emus and reviews. Also hosts some good sites.
Emu-Camp - A good all-around site focused mainly on console emulation.
Emu-Christ - Emulation without the Bullshit!
EMULAIR - In Spanish and English
Emulation Excitement - A more "polished" site with arcade and console emulation. Great for newbies.
EmuUnlim - Everything you'd want to know about emulation. Hosts an excellent news site Emulation Sphere.
Emulatronia - A great emulation site in Spanish.
EmuM@nia - In Spanish. Includes sections on arcade, console, and computer games. English mirror.
GameArchive - Specializing in flyers and posters of arcade and pinball games.
JoseQ's EmuViews - News, rumor mill, and interviews with the greats in the emulation scene.
The Official MAME Page - Get the latest on the greatest emulator. Updated sample, artwork, and high score files.
Mame32 QA - Mame32 info and art, including image, icon, and background packs.
Arcade Art Museum - Cabinet pics of arcade games.
Arcade Flyer Archive - Arcade flyers and posters of your favorite MAME games.
Brian's Coin-Op History Archive - Includes the MAME history file.
ClrMAME - Versatile rom checking utility.
GeoShock - From the dudes of neocharity, a new NeoGeo page with a different approach.
MAME.dk - Your one-stop arcade rom resource.
M.A.M.E. Links - A nice set of links.
MAME WORLD - A site dedicated to (guess what) MAME; everything but the roms.
MAMu's icons - Another set of MAME icons.
Pugsy's MAME Cheat Page - Pugsy's and the Ultimate Patchers' cheat files.
SYS2064 - Includes MAME fixfiles.
Ultimate NeoGeo Resource - Has guides info for many NeoGeo games.
Calgary Flame's NES Place - Another huge list of NES ROMs.
--- ECLiPSE EMULATiON --- - Devoted to Nintendo console systems with a large ROM list. WIBBLE.
The Emulation Embassy - Nintendo and Sega ROMS.
Fatmanuals - Provides N64 manuals in Acrobat format.
GameCopyWorld - Bootleg that damn copy-protected CD game
GameSpot - System Shock 2 Game Guide - Unreal Strategy Guide
Happy Puppy - Games galore
The Official MESS Page - The MAME of console systems