Thought I would give a

Thought I would give a quick plug to Audioscrobbler.

From the site:

Audioscrobbler started life as a Computer Science degree project by Richard Jones (better known as RJ) at the Univeristy of Southampton in the UK. The Audioscrobbler Project is an ongoing exploration into Social Information Filtering, music being the "Problem Domain".

Basically you download a winamp plugin which feeds back to Audioscrobbler what you are listening to. It builds stats of your favourite artists, songs etc... and then when its collated 500 tracks you have listened to, suggests tracks/bands that you don't have and that it thinks you would enjoy. Pretty funky. Roll on my 500nth song!!