Free online mixing platform: Burn Studios Audiotool

Burn Studios Audiotool is really cool, not only free, but also used online directly, no installation is required. It is a semi-professional music production software.

This web application uses virtual devices, including drum machines and synthesizers, to allow you to create your own infinite combinations of electronic music. All you need is a browser that supports Flash. Audiotool can download your work as MP3 or ogg.