Game Music Box plays video game music files. It works with Mac OS X and Mac OS 9. Still fairly new; please report any problems.
Game Music Box 0.5.2b2.sit or .zip (200K download)
It supports playlists, RAR, ZIP, and GZIP compression, batch recording to sound files, and uses an efficient band-limited engine for good sound quality and low processor load.
Super Nintendo SPC
Nintendo Entertainment System
with Namco, VRC6, and FME-7 sound NSFE
Nintendo Game Boy GBS
Sega Master System VGM
Sega Genesis/Mega Drive VGM