Freesound - The Freesound Project is a collaborative database of Creative Commons licensed sounds.
Hum - Songwriting for iPhone
Songcraft.io - A platform for songwriters to write, organize & collaborate.
RiffShare - Write down a musical riff, send to band members, collaborate
Horucco - Horucco is an cloud based app for musicians, songwriters, producers of every skill levelExplore chords and discover related chords on the fly.
Riffr - An audio-based social network