Tired of listening to Radio stations that might or not play what you want to hear? Try Pandora (www.pandora.com). Pandora claims it’s sole mission to be “To help you discover new music you’ll love”. The founders of Pandora have analyzed more than 60 years of music and created a sophisticated taxonomy of musical information. If you specify an artist or song, Pandora creates a unique radio station based on a Musical Genome of the song/artist/band. And to top it all off, it is completely free :). I love the sleek and simple flash interface too. I would love to take a look at how they keep up with streaming all that content across the Internet.
Update : Some Googling lead me to this article in Computerworld which speaks about some of the technology used to power Pandora.com. Looks like they use OpenLszlo.The programming approach is as elegant as the site :).