drumbit - A very easy to use drum machine.
Tinkersynth - Create and purchase unique generative art
Sampulator - Make (and record) beats on your keyboard
Type Drummer - Drum by typing
Splice Beat Maker - Make and share beats in your browser
Onemotion Drum Machine - Drum Machine is a fully-featured web-based app developed by OneMotion to enable you to create Drum Beats and patterns.