Hobnox Audiotool

I saw this at Metafilter. "A virtual 303, 909 & effects setup in your browser!"

The Hobnox Audiotool Demo is a new approach to give you a great opportunity to create music compositings online in your browser. The underlying audio engine is based on dynamic digital signal processing to provide very complex audio compositing in Flash. The graphical user interface is based on an unlimited sized desktop to layout your choosen devices as you wish to operate.

Needs Java. Takes a while to load. It's really cool though.

More on Audiotool.