Tracking Down/Header Reading
alt.spam FAQ or "Figuring out fake E-Mail & Posts"
Anti-Spam Resources
Tracking the source of email spam
WHOIS
GetNet, Inc. Traceroute
WHOIS | VeriSign
SpamSpade.org Tools
I've also made a corny program that generates as many fake e-mail addresses as you want, and places them in either a list, or generates an HTML file that can be directly uploaded to a website, so that spiders searching the web for e-mail addresses to send spam to get filled with bogus addresses. This program can be downloaded here: E-MAIL.zip (29.0kB).
And you can click here to look at 10,000 randomly generated e-mail addresses produced from this program: My 10,000 fake e-mail addresses.