Pandora is a free online radio service that allows you to build stations that match your tastes with remarkable accuracy. It's just amazing. There was a lengthy interview with the company founder on episode 6 of Inside the Net

I've built three stations so far, all based on entirely different genres. In about six hours of listening over two days, I am hearing all kinds of music that I've never heard before -- and it's all stuff that I like.

So much for free. Pandora is going to cost me a fortune!