The Spam-L (see abuse.net/spam-discussion list is the Internet's one best source for information about spam, how to deal with it, and the latest state of play. A peerless FAQ (Frequently Asked Questions), filtering solutions that actually work, how to read email headers so you know where a mail came from, spam legislation news: if you're interested in spam, and you should be, this site has everything.
CAUCE at www.cauce.org is the Coalition Against Unsolicited Commercial Email, which is well worth visiting also.