Nestopia is a cross platform Nintendo NES Emulator
Nintendo NES Emulator
Windows:
Nestopia v1.40 Binary
Nestopia v1.40 Language Pack (last updated 21 June 2008)
Nestopia v1.40 Source Code
Linux:
Nestopia Linux
Mac OS:
Nestopia Mac OS
Nestopia is the current king of the NES emulation hill. It uses highly optimized cycle exact emulation, allowing it to run titles that rely on precise timing, many of which break under inferior emulators. This accurate emulation does come at a cost; Nestopia requires a minimum of a 600MHz machine for full speed; but if you have one, this the best available NES emulation for Mac.
http://nestopia.sourceforge.net/downloads.html