Mesen - Mesen is a NES/Famicom emulator and NSF player.
Nestopia - A portable and cycle-accurate NES emulator written in C++
VirtuaNES - VirtuaNES is Famicom/NES emulator for Win32.
FCEUX - FCEUX is a Nintendo Entertainment System (NES), Famicom, and Famicom Disk System (FDS) emulator.
RetroArch - RetroArch is a frontend for emulators, game engines and media players.
puNES - PuNES is a high accuracy NES emulator.