GoatTracker - This is a crossplatform C64 music editor.
Synthesia - A fun way to learn how to play the piano.
OnlineSequencer.net - OnlineSequencer.net is an online music sequencer that allows users to create beats and music tracks.
Playground Sessions - Online piano learning game.
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.
Piano From Above - Piano From Above is a program that turns learning the piano into a videogame.