Spotalike - Spotify playlist with similar songs, according to Last.fm
Spotify - Map shows when two people play same song at same time
MusaicFM - An iTunes like screen saver based on Spotify and Last.fm
DiscVibe - Create personalized and contextualized Spotify playlists
Bowtie - Bowtie is a desktop accessory that allows you to see and control your music (iTunes, Spotify...
Ranked Records - Create Spotify playlists with all an artist's songs