If you have ten bucks to spare, and you like games where your songs are featured, then this game is the jackpot.
Audiosurf takes your songs (as in songs YOU actually have, like in MP3 or CD form) and makes a track based off them. At calm moments, it will go slow, uphill, and have "cool" colored blocks (purple and blue). At intense moments, it will be fast, downhill, and have a lot of "hot" colored blocks (like red). What you do is you crash your "car" into the blocks to collect them, and try to get matches of three or more.(a la
Klax) The "hot" colors are worth more points than the "cool" colors.
Finally, to top it off, you register a free account through the program and you can compete for highscores on your favorite songs.
Store page is here:
http://store.steampowered.com/app/12900/