In case you didn't know, this pretty slick little game came out over Valentine's day, and let me tell you. This is probably one of the best music related games that I've enjoyed since DDR (Sorry, Guitar Hero isn't really my cup of tea)
It's kind of like a mash up of F-Zero, tetris, and Frequency. You can upload whatever music you want (much to my surprise, even in formats like .ogg and .flac ^_^) and 'ride' along the track, making clusters of similarly colored blocks and getting points to flex your e-peen on the leaderboards.
The game is also one of the first titles that has taken advantage of the recently released Steamworks so rock on Valve, helping out the little guys.
There's a demo available on Steam, you can play for ~1 hour before it prompts you to buy the game, and it's only $10. So go on! Try it already!