Spotalike - Spotify playlist with similar songs, according to Last.fm
Owlead - Grow your Twitter with valuable followers, effortless
Bowtie - Bowtie is a desktop accessory that allows you to see and control your music (iTunes, Spotify...
Sound Control - App-specific volume control
Magic Playlist - Get the playlist of your dreams based on a song
EarTrumpet - Volume Control for Windows