If you trek
over to SamSpade.Org, you'll find a useful tool
assortment to track down spam
mers and idiots, just like Humphrey Bogart
in the Maltese Falcon
would do for you if you paid him (and dug up his body
and re-animated him, but I digress).
SamSpade.Org can help you find someone online using a large assortment of tools, such as:
The Address Digger: Use traceroute, IP Block and Whois.
Find Obfuscated URLs
A Safe Web Browser
A Java Pad
A reverse-DNS Lookup
A DNS Query for items like mailgates, etc.
A Blackhole Checklist
Plus many other tools. They have things set up as a free service. These tools can help find spammers or idiots who send you annoying emails (like threats, etc.)