I have to second the Machinarium soundtrack. It's one of the few I listen to on a regular basis. The Witcher is another fantastic soundtrack. Medal of Honor has a pretty good one as far as FPS games go.
However, if there's one game I'm desperately wishing would release the soundtrack it's Portal 2. You can hack your way into the game and grab the audio files (which are WAV, thank you Valve!) but I'd prefer a polished soundtrack I could grab. The music is wonderful, though.