A friend of mine wrote:
I had the unpleasant experience of receiving a spam for a kiddie porn site,
and I had to ask around and do some research to learn where I could turn in
these perverts.  Here's what I learned if it ever happens to you.

Someone suggested I check out SamSpade.org and its free software for tracking
email to its real source as well as finding out the owner of specific sites.
The software is only for Windows systems so my Mac and I couldn't use it, but
I was able to paste the URL for the kiddie porn site into one of their online
tools and got an incredible amount of information.  I also found out the site
used for the spam is owned by the same London-based company so forwarding it
to their abuse address was worthless.

I also forwarded the email to uce@ftc.gov to alert the Feds about these
sleezebags.

I then tried several search engines which promptly gave me links to sites
with kiddie porn, not sites to report kiddie porn, so I tried Ask Jeeves and
got the link to the National Center for Missing and Exploited Children.  They
had a link to missingkids.com and a cyberspace crime reporting site.

The form I filled out was confusing so I hope I didn't report myself as a
pervert.  <G>

You may want to bookmark these links in case you ever receive filth spam like
that or you become aware of a site aimed at luring children to harm.

The National Center for Missing and Exploited Children http://www.missingkids.com/

Sam Spade.org http://Samspade.org

Children's Protection & Advocacy Coalition http://www.thecpac.com/stop-it.html

AOL is setting up an Amber Alert site and system which appears to be open to non-AOL users.  You may want to add that.  One of the local tv stations has set up links to this information which you may want to check.  Working for You http://www.wfmy.com

Children's Protection & Advocacy Coalition http://www.thecpac.com/stop-it.html