I was going through the Independant Games Festival Contenders for this year's Audience Choice Award (only now do they have download links up) and one of the games I tried was Audiosurf, a game that I had heard previously about, but thought the developer was doing the whole 'we are awesome speel' that seems to come out of the mouth of every sane developer in the industry (it is getting harder and harder to tell when they are talking BS or not). But in this case Audiosurf is awesome, and everything it was said to be.
You start by selecting an audio file on your computer, Audiosurf identifies the various musical aspects of the file, generates a level and then you play in that level while the music you selected is playing. You play the game either with a mouse or 360 controller by trying to connect coloured blocks on a grid while avoiding gray blocks.
It is awesome and supposedly out at the very end of next month, possibly through STEAM. But until then I highly recommend the Demo, even if it does yank the game from under you after a few songs.