Playmoss - Create playlists from YouTube, Vimeo and SoundCloud
22tracks - DJ curated Spotify playlists on iOS
podsync - Simple and free service that lets you listen to any YouTube or Vimeo channels, playlists or user videos in podcast format
Spotify - Map shows when two people play same song at same time
Audioship - Upload audio to YouTube or Facebook
8tracks 3.0 (iOS) - Refreshingly human music playlists