Playlist Machinery - Tools that help you create & organize your Spotify playlists
Slackbox - Spotify playlist collaboration through Slack
Playmoss - Create playlists from YouTube, Vimeo and SoundCloud
podsync - Simple and free service that lets you listen to any YouTube or Vimeo channels, playlists or user videos in podcast format
Jelly Party - Watch anything together.
Audioship - Upload audio to YouTube or Facebook