FCEUX is a portable and highly accurate NES/Famicom/Famicom Disk System emulator with excellent compatibility with almost every rom dump available, supports both PAL and NTSC modes, save states, game genie support, and networking. FCEUX also offers tools for debugging, rom-hacking, map making, Tool-assisted movies, and Lua scripting. Finally FCEUX includes a GTK2 GUI to assist in configuration and gameplay.
WWW: http://fceux.com/