hmm..the webjay looks interesting, but the site is very slow for me right now...
I'm on audioscrobbler -
http://www.audioscrobbler.com/user/keyshawn
- it's a free plug-in available for xmms, winamp, itunes, and whatever else you use to play music on your comp. it takes the data the music that you play and creates a list of how many songs you've played, what's popular, what artists have you played the most, etc. The variety of data and personalization of that data has such capabilities to be mined [for advertising]; it's actually kinda scary, imho. It can though, be used in a more healthy fashion - for example - on audioscrobbler - what other artists are you interested in and who else shares the same taste in music.
It's just a matter of time before it's expanded to use the data on your digital audio player, or even webradio [however, the logistics for that would be pretty crazy].
catcha back on the flipside,
keyshawn