Via /. comes this mention of research at HP that is tracking the propagation of memes in blogs.

It would be nice to see something like this become dynamic and available as a real-time resource. It's interesting to see how memes like the visited states meme take off, and the possibility of being able to track a meme back to its sources seems interesting as well. The research only targets URLs, which does not fully constitute a meme, but it should provide interesting results. Maybe in the future someone will be able to track an meme across links/comments/trackback/etc...