Napster is apparently under-fire by the RIAA (big surprise). In case you've been under a rock, Napster is an impressive use of the internet to create a virtual database of MP3s. Shawn Fanning, the creator, speaks out about Napster's future. Of note, he hints at expanding Napster to files other than MP3's. :) If he thinks they're in trouble now...
There's a great Mac port, known as Macster.