Nestopia - A portable and cycle-accurate NES emulator written in C++
Roms Mania - A working online resource for roms.
Mesen - Mesen is a NES/Famicom emulator and NSF player.
KillerRoms - Download free Video Games ISOsa nd ROMs!
FCEUX - FCEUX is a Nintendo Entertainment System (NES), Famicom, and Famicom Disk System (FDS) emulator.
ROMNation - Rom download site