Noiseblend - One-tap music for every occasion, with Spotify Premium
Magic Playlist - Get the playlist of your dreams based on a song
cmd.fm - Command-line radio for geeks
Spotalike - Spotify playlist with similar songs, according to Last.fm
Noon Pacific - The week’s best music handpicked & delivered to your devices
Playlist Machinery - Tools that help you create & organize your Spotify playlists