Turntable.fm - Turntable.fm is a social media website developed by Billy Chasen and Seth Goldstein that allows the audience to stream their own music.
CyTube - Free, open source synchtube
Bandlab - Capture, nurture, and collaborate on song ideas in the cloud
Metastream - Watch streaming media with friends
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.
SyncWatch.Video - With SyncWatch you can watch videos and listen to music in sync with your friends. Just create a room and start watching! SyncWatch is free and no login is required.