Pandora

Thanks to Bogomip for the link - this site is actually quite impressive - the only catch I've found so far is in finding some of the more eclectic tastes of the world that I've come to enjoy. (Some Japanese Rock, Scottish Folk, and Classical names like Mozart seem to be missing. )

Even though it may be limited the songs that are available are fairly high quality and the features list on the player seem fairly intuitive. Not to mention the selection it does come up with a fairly nice selection of variations on a theme based on the single name you put in at the beginning to create individual 'stations'.

Pandora's definitely worth a link on the side and maybe an account.