Just starting to use the music discovery site Deezer. A bit like Last.fm but Deezer finds whole albums rather than just single tracks. You lose some of the whimsical choices of Last.fm but gain the ability to have Guns & Roses afternoons. The site also has a clean interface with some neat controls. The ad positions are a bit clunky but you can't have everything.
I have been a big fan of Last.fm over the last year, Check my stats! but I feel very warm towards Deezer at the moment