Game Center - Game Center brings social gaming to OS X and iOS apps.
Roms Mania - A working online resource for roms.
GameStreamer - Connection people and games anywhere.
Gamulator - Gamulator is the n.1 place to find and download all the retro roms, iso's and games for your arcade emulator.
OpenGameArt.org - A site dedicated to sharing artwork & other assets for game development.
CoolROM - Download from the largest and cleanest ROMs and emulators resource on the net. Mobile optimized. Systems include N64, GBA, SNES, NDS, GBC, NES, MAME, PSX, Gamecube and more.