Clone Hero - Clone Hero is a free rhythm game, which can be played with any 5 or 6 button guitar controller...
keezy - A colorful soundboard. Play with music.
StepMania - Rhythm game for Windows, Mac, and Linux.
SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
Osu - Osu is Music, Rhythm, Single and Multiplayer video game developed by Dean Herbert.
Aftertouch - Aftertouch – 3D MIDI Controller created and published by Kevin Nelson.