Fascinating stuff: "Rainbow is a program that performs statistical text classification." It can use Bayesian classification to automatically categorize documents.

Jon Udell tried it out last year: " There's been some discussion in the blog world about using a Bayesian categorizer to enable a person to discriminate along various interest/non-interest axes. I took a run at this recently and, although my experiments haven't been wildly successful, I want to report them because I think the idea may have merit."