http://www.bannister.org/software/ao.htm
It's called auido overload, and it allows you to rip sound files (music and sfx) from ROMs of these systems:
* AY - Amstrad CPC/Spectrum ZX
* GBS - Nintendo Gameboy
* GSF - Nintendo Gameboy Advance
* GYM - Sega Megadrive/Genesis
* HES - PC Engine
* KSS - MSX
* MDX - Sharp X68000
* MOD - Commodore Amiga
* NSF - Nintendo NES
* RAW - PC with AdLib
* SAP - Atari XL/XE
* SNDH - Atari ST
* SPC - Super Nintendo
* VGM - Sega Master System/Game Gear
* YM - Amstrad CPC/Spectrum ZX/Atari ST
I've used it more than once or twice. It's a must-have if you want to get a high-quality soundtrack from a game, or get rare sound effects.