Spotalike - Spotify playlist with similar songs, according to Last.fm
SubmitHub - SubmitHub makes it easy to contact music bloggers, Spotify playlisters, record labels and more. We give you all sorts of statistics and ways to filter who to send your music to.
Magic Playlist - Get the playlist of your dreams based on a song
Playlist Machinery - Tools that help you create & organize your Spotify playlists
MySphera - When music promotion met micro-influencers
Doppler for iPhone - A better offline music experience for iPhone