I recently discovered that an E Book I was selling had been pirated and had been put on a file sharing site. A friend had searched for it and the pirated copy ranked in front of mine! The file sharing site had a policy of taking down pirated material if you could prove that the material was yours, but after several attempts and no replies from them, I started the process with Google. I had heard mixed reports about the effectiveness of the process, but it was very straight forward. Just answer a few questions such as which Google application does your material show up on, where is the original material (in my case it was on a website I own), was I the legal owner and a couple of other things. I checked the file sharing site about a day later and my book was no longer available. Success! The moral of the story is, DMCA is an effective weapon with which to protect yourself against Pirates. Google may not be the only search engine, but people pay attention when they say "Naughty Naughty" Good Luck AP
If you don't hear any reply from the websites owner, you can email the datacenter on which that website is being hosted. Provide enough proofs that you are the actual copy right owner and they will either warn that pirate website or take it down from their servers.
Both good ideas and I probably would have gone down that route if the Google thing hadn't worked so fast.
I recommend you to take a look at this list of actions http://www.plagspotter.com/defend-your-site-from-plagiarism/ quite helpful when you have found someone stealing your content and you don't know what to do.
Another great tip. I've heard people moaning in the past that there is nothing you can do about piracy, but clearly there are effective courses of action that allow you to take back control of your property.