Reading Email Headers (http://www.stopspam.org/email/headers.html)
It's essential to know how to access and understand full email headers in order to expose phishing and scam emails.

Limiting Unsolicited Bulk Email (http://www.imc.org/imc-spam/)
Anti-spam resources include papers examining the problem of bulk e-mail and links to other organizations.

Spam Laws (http://www.spamlaws.com/)
United States, European Union, and other countries' laws and pending legislation regarding unsolicited commercial email.

SpamArchive.org (http://www.spamarchive.org/)
Database of known spam to be used for testing, developing, and benchmarking anti-spam tools. Accepts user contributions.

Spamfaq.net (http://www.spamfaq.net/)
FAQs from news.admin.net-abuse.email and related newsgroups including information on how to filter and report spam, as well as information on the anti-spam community.

The Spam Letters (http://thespamletters.com/)
Replies to spam, organized by category.

Ending Spam with An MTA Acquaintance Protocol (http://www.w3.org/2003/10/acquaintance-protocol/)
Just a cool idea, talking about a computational challenge to make spam uneconomical.

Meng Wong's Perspectives on Antispam (http://it.slashdot.org/article.pl?sid=06/02/15/2358256)
a big thread started by Meng Wong blog entry Internet Governance: An Antispam Perspective (http://www.circleid.com/posts/internet_governance_an_antispam_perspective/)
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MSExchange.org anti spam section (http://antispam.msexchange.org/)
(links to articles)

Technical Responses to Spam (http://www.windowsecurity.com/whitepaper/anti_spam/Technical-Responses-Spam.html)
In response to the growing torrent of unsolicited bulk email, many technical schemes have been proposed and implemented to distinguish spam from legitimate mail and to block delivery of spam while letting legitimate mail through. Although none of the schemes is the "magic bullet" some of them, particularly when used in combination with each other, can help limit the amount of spam that users receive. Those are discussed in this whitepaper.