Webmaster Tools - Copyscape
Most people work hard on their websites and the last thing you want to find out is that someone has taken your hard work and reposted it somewhere else on the Internet without your permission. Unfortunately, this happens more than we would like.
One of the tools I often use to check and see if my sites have been copied is Copyscape. They offer a free service that returns ten results and a premium service that you can pay for that offers unlimited results.
I checked three sites with it today, and Copyscape found copies of content from two of the three in other places on the Internet. The first was this blog, and it accurately found that there is a copy of the latest blog post on my main company site www.lgr.ca. I checked a friends blog and it found several copies of some of the content on three other sites. The content was not actually copied from the site, but was a movie quote that several others have quoted exactly as well. The third site I checked is actually still in development, so it came back with no content being similar to other sites, which makes sense since it is original and never been on the Internet.
Copyscape, is also a very useful tool if you are looking at purchasing a website from one of the webmaster forums, like DigitalPoint Buy, Sell or Trade section. You can use it to check websites you might be interested in to see how unique the content actually is, if it is simply being scraped from other sites, or maybe just borrowed from Wikipedia. It is not 100% fool proof, but it will give you a good idea if the website and the content are worth purchasing.
Overall Copyscape can be a useful webmaster tool to check the Internet for copies of your content. I know I check my sites occasionally just to see if any of them have been copied and used without permission.