Ocean beta - Make music with friends in your browser
Sampulator - Make (and record) beats on your keyboard
iO-808 - Rhythm composer modeled after Roland's TR-808 drum machine.
Auxy Music Studio - Auxy brings real music creation to iPhone in a simple and inspiring format.
Cameo - Book personalized video shoutouts from your favorite people
Ramsophone - A generative art/music machine. (Be sure to refresh!)