Playmoss - Create playlists from YouTube, Vimeo and SoundCloud
Momixa - Pick two songs and get the perfect mix
Playlist Machinery - Tools that help you create & organize your Spotify playlists
Music Suggestions Ninja - Enter an artist's name & find similar, lesser known artists
Audioship - Upload audio to YouTube or Facebook
Boil the Frog - Create a seamless playlist between any two artists