I'm fairly sure I'm the last person on the internets to find out about Pandora, but on the off chance you're even further behind the curve than I am…
Pandora is sort of like a custom radio station that is aggressively marketed to a single-person demographic (i.e., you), or an artificially intelligent jukebox that tries to follow up your initial selection with other stuff you'll like. It also learns from your feedback -- "I like it," "I don't like it," etc.
For instance, I went there and tried entering "Maria Schneider" as the artist. I didn't offer any feedback, I just let it play for a while to see what it would come up with. Here's what I got:
"Nocturne" - Maria Schneider, Allegresse
"New Leaf" - Drew Gress, 7 Black Butterflies
"Concierto de Aranjuez," Miles Davis, Sketches of Spain
"Orbits" - Wayne Shorter, Alegría
"Thieves and Poets Part 3" - John McLaughlin, Thieves and Poets
"Journey Home" - Maria Schneider, Allegresse (okay, evidently since Pandora calls this "Maria Schneider Radio," it's going to play Maria's stuff with more regularity than the others)
"Dizzy's Business" - Dizzy Gillespie Big Band, Birks Works
"Discipline" - Sun Ra, Space Is The Place
"Ad Lib On Nippon" - Duke Ellington, The Far East Suite
"Hiroshima Memorial" - Dave Liebman Big Band, Beyond The Line
"Todo Modo" - Mingus Big Band, I Am Three
"Zulu" - Tony Lujan, Zulu
Not bad at all, I thought. Of the tracks I wasn't already familiar with, I thought the McLaughlin was a long way from John's best work, the Liebman was beautiful and very different from other things I've heard from him, and the Tony Lujan (who I've never even heard of) had strong writing and playing, but never quite grabbed me.
Anyway, you can create up to 100 different "stations," each based on either an artist or a specific song, and each independently customizable. And it's free! (Apparently, the free version is ad-supported, but I haven't heard any yet.)
This is definitely a fun toy. If you try it, make a note of your results and post them in comments.
EDIT: I let it play a little longer, and I got "Piece One," from Anthony Braxton's out-of-print 1976 record Creative Orchestra Music. How cool is that?