TubeLister - Generate a YouTube playlist from your opened tabs.
Openwhyd - Collect and Share the tracks you love.
DiskyT - Youtube playlists done right
SoundClick - SoundClick is a music-based social community.
OrganizeTube - Create video playlists from Youtube, Vimeo and other sources
Music Smasher - Find any song. Music Smasher searches Spotify, Rdio, SoundCloud, Bandcamp, and YouTube.