http://spamcop.net

You can register with Spamcop for free, get an ID, and forward all spam messages (full headers) to Spamcop. They automatically trace the originis of the offending spam message, send a report to you, and you click on where to send the report, and it forwards it to the where it really hurts the spammer: their own internet provider.
Also forward all spam messages to:
UCE@FTC.GOV

This is a US Government address.
They are attempting to determine the extent of email fraud, although I doubt they understand the extent of spam.
For now, they are investigating various fraud and/or scheme scenarios, but they are still asking that ALL spam emails be forwarded to them.
stock fraud

If you’re solicited with stock/securities promotions, please forward the offending email to:

enforcement@sec.gov
cyberfraud@nasaa.org
isfeedback@nasdaq.com

These are US government/trading organizations who want to know of any potentially shady deals. You are encouraged to forward any mailings which include stock/securities buy recommendations.
complaints.detroit@fbi.gov

Forward all child pornography messages to the FBI at the above address.
otcfraud@cder.fda.gov

Report drug scams here if directed to a USA addres, the FDA wants to know of potential drug scams.
419.fcd@usss.treas.gov

Report Nigeria-letter scams to the above addy.

http://www1.ifccfbi.gov/cf1.asp

Direct other internet scam complaints to the above website.

Source: Anti-spam