AMPLI.FI - Live online music community. Twitch for tunes.
Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
Soundscape - Sync your music with the open source community
Kompoz - Kompoz is an online platform for crowd-sourcing music creation, making you record, create or publish music with the guidelines of a world-class musical expert.
Krue - Twitch for music: live streams from amazing musicians
Encore Music - An open source, extendable music player for Android.