I've recently stumbled on the site Musicovery.com which is an online flash based music player.
Unlike other music streaming sites like Dizzler. Musicovery allows the user to set the Year range, popularity, genre, mood and beat filters only; it then searches all the related music randomly and plays it. The nice thing about it is it shows the generated play list in visual mode and shows the relation from one to the other as lines similar to Yahoo pipes.
An added advantage for me is that it only eats up 10-20kbps of my bandwidth which is low enough so I can just freejack on open Wifi APs without being noticed!
Note: As you can see in the attached screen shot, I'm rediscovering the 80's!