If you think you may be the victim of a crime involving your computer or Internet, you should report it as soon as possible to one of the following Law Enforcement agencies.
Even if you are hesitant to report the crime immediately, take a few minutes to preserve any evidence you may have by saving email or files to an off-line medium like a USB drive. Also, if the evidence you have is ephemeral, use a “Print Screen” feature available to most Operating Systems to capture the data before it becomes unavailable (i.e. Chat room dialogs). Should you decide to report the crime later, you will be thankful to have some useful information to provide to Law Enforcement.
Your Local FBI Office:
http://www.fbi.gov/contact/fo/fo.htm
The Internet Crime Complaint Center:
http://www.ic3.gov/default.aspx
Computer Crime & Intellectual Property Section
United States Department of Justice:
http://www.justice.gov/criminal/cybercrime/reporting.htm
National Center for Missing & Exploited Children:
http://www.missingkids.com/
United States Computer Emergency Readiness Team (for technicians):
http://www.us-cert.gov/
Regardless of your expectations, you should seriously consider reporting any crimes because it enables these organizations to better evaluate the extent of the problem.