TubeLister - Generate a YouTube playlist from your opened tabs.
Plexamp - A small music player with a number of unique features
Playmoss - Create playlists from YouTube, Vimeo and SoundCloud
Vinyls - Vinyls is a music player that lets you listen to your music without any complicated setup.
DiskyT - Youtube playlists done right
Poolside FM for iPhone - A pool party in your pocket