If you want a one stop shop, don't mind torrenting a 6gb file, and don't mind getting a bunch of other roms as part of the iso this torrent is pretty great:
http://thepiratebay.se/torrent/6144865/6666_in_1[ROM_PACK]_RETRO_LEGENDS_[NES-SNES-NeoGeo-GBA-Mame-Sega
It does work as advertised, i...