Okay a widget is an addon to opera. If you don't have the opera browser it's worth downloading just for this even if you won't actually use it for browsing.

This fantastic application will recommend (and play) music based on your tastes. You type in various songs and artists that you enjoy, and it will consider everything you have entered into your "channel" to generate playlist with songs it thinks you will like. I have to say it recommended some GREAT artists that I really enjoyed that I never heard of before. This thing is great!


Opera can be downloaded here:
http://www.opera.com/download/


Pandora can be downloaded here:
http://widgets.opera.com/widget/3765/

I prefer last.fm, has more features (and music?)

Really? Hmm thanks for the tip I'll check into it.