1. Burn a copy of your site and there site to a CD - send it to yourself registered mail - do not open it as the dates can serve as evidence in court later (never actually plan on going to court, but this helps your bluff)
2. Write a cease and desist letter to them. Tell them about (1) and you are prepared to use it.
3. Write to their host. Tell them about (1) and that they have 48 hours to take the site down or you will name them in legal action against the site (this usually works as it in the small print of most hosts ToS)
4. Lodge a DMCA complaint with Google:
http://www.google.com/dmca.html (this usually works well as well). Lodge a copyright complaint with Yahoo:
http://docs.yahoo.com/info/copyright/copyright.html and MSN:
http://search.msn.com/docs/siteowner..._AboutDMCA.htm
CBP