Noisli - Noisli is a fantastic background noise and color generator for working and relaxing. Online soothing ambient sounds like White noise, Rain and Coffee Shop.
Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
Noizio - Feeling that the noise of the big city is too much for you to bear?
Frets on Fire - Bonus content.
zenmix.io - Ambient background sound generator
StepMania - Rhythm game for Windows, Mac, and Linux.