Vidlis - Create music playlists from YouTube videos.
Playlist Machinery - Tools that help you create & organize your Spotify playlists
DiskyT - Youtube playlists done right
Poolside FM for Mac - An infinity pool of summer sounds in your Mac menu bar
OrganizeTube - Create video playlists from Youtube, Vimeo and other sources
Listen for Mac - Add songs to Spotify playlists using keyboard shortcuts