Source: http://lifehacker.com/5550778/soundation-studio-is-a-flash+based-music-mixer
If you've ever had the urge to mess around with mixing your own electronic music, Soundation Studio is a free Flash-based editor that makes editing and mixing your own songs drag and drop easy.
Soundation Studio is simple enough that you can start mixing together a song with absolutely no experience or technical knowledge. If you're inclined to do so you can dig into the sub-menus in Soundation Studio and tweak any of the dozens of variables available—variables you may, if you're as much a novice in music mixing as I am, have to look up.
You build your song up from the hundreds of samples included in the Library or use the virtual instruments to create your own beats. When you're done you can export the song as a .WAV to your computer or save it on Soundation Studio and share it with a link. Soundation Studio is free and only requires a login if you wish to save your projects between sessions.