OnlineSequencer.net - OnlineSequencer.net is an online music sequencer that allows users to create beats and music tracks.
SoundGrail - SoundGrail Music App designed for pianists, guitarists, and DJs.
GoatTracker - This is a crossplatform C64 music editor.
keezy - A colorful soundboard. Play with music.
Jummbox - A modified Beepbox that have more stuff then Beepbox. It can be used just like Beepbox. The features of Jummbox is the same of Beepbox's features, but Jummbox have more stuff to offer.
Splice - Music creation, collaboration, and sharing made simple.