Factotum is compatible with 16 awesome music servies: Rdio, Grooveshark, Hype Machine, Pandora, Last.fm, Napster, Playlist.com, Live365, BBC iPlayer, Songza, Jango, We Are Hunted, Deezer, thesixtyone, and Blip.FM.
To use Factotum, just hold Option + Shift and press your Mac's media keys. It works as expected! Currently works with both Chrome and Safari. More browser support soon!