Matt Croydon has written a simple TrackBack implementation in Python. As Sarabian points out, that'd be a rather neat Vellum plugin. That said, it would need a fair amount of documentation about where to put all that RDF in your templates. I need to start bundling docs with plugins, I think.
-----This website belongs to Stuart Langridge. Contact details are available. Don't eat yellow snow. Valid HTML5, at least in theory, except for the bits that aren't because I'm that futuristic that I'm ahead of the spec, oh yes. HTML5 help from Bruce Lawson, among others. Fonts from the superb FontSquirrel. End.