Audio-Surf is a Music game, in which you can give it any music track on your computer. It will turn it into a roller-coaster type track that will rise (slow) and fall (speed up) with the tempo of the song. Coloured blocks fly at you to the beat and melody of the song, and you must collect and form combos with them while avoiding the grey ones.
It says the final version is coming in February, but you can sign up to get a weekly beta release on the site. Some people have uploaded copies of the beta version to their own servers so you can access it any day of the week, but download at your own risk.
Any-one heard of/been playing this game?
Post what tracks you've found work well in game, if you can.