Old Welsh Guy (James Edwards) has a great post on catching and dealing with content thieves – those unscrupulous folks who steal other people’s content and attempt to pass it off as their own. It has happened to me several times and I have dealt with them in a similar manner.
A few excerpts:
The instant you create anything, YOU own copyright to that material. Technically you own intellectual property rights on it. These are legally enforceable rights that YOU as the owner can enforce.
Anyone concerned about content being stolen should use www.copyscape.com. this will throw up any duplicate content issues. Then you will know the site that has stolen your content.
Tell them politely that as the copyright of the content is yours, you intend to enforce your legal rights should they not take the requested action within the agreed time.
There’s a lot more good stuff there including what evidence to gather as well as who you should contact in addition to the thieves themselves.