check out pandora


www.pandora.com
this is a wonderful free program that builds your own personal radio stations according to your likes and dislikes for jazz and popular music.
I stream it to my airport express via a program called airfoil.
check it out!
fidelio101
here's an informative article comparing pandora to last.fm

http://www.stevekrause.org/steve_krause_blog/2006/01/pandora_and_las.html
I have this subscription and find it useful when I'm just dodging in and out of the room. Every now something catches my ear and I buy it - a bit like downloading mp3s from the internet - a good sampler, but better filtered!

It doesn't work for classical music though as far as I have found.
I find both Pandora and Last.fm to be great for finding new music.

On the Mac, the Last.fm player is invasive. Any time it opens, it resets the Audio Midi Setup to 2ch-16bit and 44.1Khz. (I like to up-sample iTunes to 48Khz to 96Khz).

Last.fm also wants you to install a piece of software called Audioscrobbler that continually tells them what you are listening to on other players. I don't like the idea of that.