I've been looking around AudioGalaxy (with the Linux client) and it's brilliant.
For instance, I just found out that there's
a lot of Field Mice stuff listed, including long-deleted vinyl-only gems (songs like Humblebee, Song 6 and so on); not to mention live Slowdive tracks (albeit some let down by dodgy MP3 codecs), Lush rarities and even some Paradise Motel (other than their cover of Drive, that is).
The range is much wider than on KaZaA, which is mostly widely available things.
Which is good if you're a teenage mook wanting to pirate the latest rap-metal
hit, but not so good if you're a dedicated trainspotter looking for obscure
old singles and mixes.