I have heard about in the past but have neglected to get on the bandwagon. This review from has inspired me to get my music loving ass over there and see what the fuss is all about. Its similar to the intelligent recording setup in SageTV, in that you tell it what you like and it will start streaming music you like. If you don't like it, you tell it not to play that song and other songs like it. Currently there are over 400,000 songs available, that should keep you busy for a day or two.

From the article:

The playlists are occasionally repetitive, especially in narrowly defined
stations where songs are closely related. In an effort to branch out, Pandora
will occasionally take a minor feature in one song and choose another song in
which it's a major feature. Thus, a short metal guitar riff in an
otherwise-quiet song brought up an Ozzy Osbourne assault, which I quickly
assigned to an Early Oz channel. But for the most part, we continue to be
delighted by Pandora's seemingly intuitive—and even counterintuitive—leaps. I
built an endlessly and surprisingly eclectic station around just two artists:
the "alternative rock" band Cake and a folk-pop act, Innocence Mission.