Sampulator - Make (and record) beats on your keyboard
Helio - Design successful products by revealing key user behaviors
Splice Beat Maker - Make and share beats in your browser
SongMine - Songmine is a free online tool for discovering and recording chord progressions with your favorite DAW.
BlokDust - Join blocks together to build sounds with this web-based music making app.
Blocs Wave - A free audio app for creating music loops.