A Greasemonkey script to add Spotify links to artists in Paul Lamere's SXSW Artist Catalog:
→Install←
Also, here's a CSV version of the artist list.
An aside: Spotify are keeping very quiet about the P2P network behind their music client. It's not a secret (sites with an interest in P2P cover it, and it's been there for years) but isn't mentioned at all on spotify.com, in the client itself, or in the mainstream news reports that are being published this week [Guardian, Telegraph]. The only indication I noticed was when OS X's firewall asked if Spotify should be allowed to accept incoming connections.