Some of my favorite game soundtracks:
Cubixx HD - the best I've heard by far! Some great dubstep/electronic songs.
Mercury HG - electronic/dance (really fun, but can get distracting when playing certain levels lol)
Wipeout HD - classic fun electronic music (one of my first favorites)
Shatter - this is another cool soundtrack with airy electronic beats
Groovin Blocks - also very upbeat with some fun, quirky songs
What are your favorites?