I was actually looking for a tool that would allow me to easily see who was pulling the RSS feeds from certain sites and came across Copygator instead. Whilst the original search was not for content theft per se, but rather to discover where content is being syndicated, this seemed a useful tool.
Copygator constantly monitors RSS feeds to see if blog posts are reproduced elsewhere, and then lets you know. Over 250 million blog posts have been compared to date.
This led to urlfan.com which lists the most popular websites and finds Web 2.0 properties that have linked to you.
Has anyone used either of these before? Do you have any comments on them, or suggestions for similar tools?