One day I’ll need to come up with a big list of sites that track memes, especially those that do so automatically or semiautomatically (as opposed to sites like Metafilter and half the weblogs in the universe that track memes all the time by virtue of their infectious passing of memes from one to another).
The latest is the coolly named (yet awkwardly spelled) Memeufacture.
The set of categories included is somewhat strange, but I assume it will grow. Right now your choices are Influential, Politics (Right), Politics (Left), Apple, and Law.
