Also see Getting Rid of Spam in the Did You Know section of Webopedia.

ROKSO Home Page 
Database of known spammers who have repeatedly violated ISP's anti-spam regulations.

The Spamhouse Project
An organization that works with ISPs to identify and remove spammers from the Internet.

Eye on Spam
Powerful weapons have emerged in the war against spam, so why isn't the problem going away? A 2002 Datamation article.