http://www.junkbusters.com/harvesting.html#government

If the spam involves fraudulent or deception practices, you can forward it to
uce@ftc.gov for the Federal Trade Commission to add to their database

If a Nigerian says they have millions of dollars waiting for you to collect,
forward the email with the subject "419 sample - no financial loss" to
419.fcd@usss.treas.gov for the US Secret Service to investigate.
Nigerian Advance Fee Fraud (also called 419 Fraud) has been going on since the
80's with faxes, and has recently become common with email. If you receive
faxes for this, forward to the USSS on 202 406-6930 with a cover sheet giving
your contact details and stating "no financial loss".

419.fcd@usss.treas.gov subject "419 sample - no financial loss"

http://www.caag.state.ca.us/donotcall/index.htm