Copyscape is a search engine of sorts that uses Google Web APIs to find copies of your content on the web. This can help you manage your copyrighted works and find violators of your copyright policy. The service is currently in beta testing but it’s globally accessible.
I’m sure that Copyscape won’t capture everything but it did find a few of my works being copied on other web sites. I’m happy people think my content (not necessarily on chrisshort.net) good enough to copy however; it’s against the law and violates my copyright policies.
Copyscape is a good service and I’m sure there will be many improvements on the service before it comes out of beta status. If you’re worried about your work(s) being plagiarized Copyscape will help you find copyright violators quickly.