OnlineSequencer.net - OnlineSequencer.net is an online music sequencer that allows users to create beats and music tracks.
Clyp - Clyp is the easiest way to record, upload and share audio. No account required.
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.
Audio Hijack - Record any audio, with Audio Hijack!
AudioSauna - AudioSauna is a full-featured audio workstation for making music online.
Loopback by RogueAmoeba - Get all the power of a high-end studio mixing board, right inside your Mac!