Thunderjudge
Now that Paragrasp has reached a point of relative stability, I'm going to be slowing down development efforts on it, and start on my new project. Here's Thunderjudge, and extension for Thunderbird that adds a general statistical classifier that automatically sorts mail into user defined categories based on word frequencies. It basically extends the bayesian spam filter to apply to any number of categories, as described by Ben Kamens which he implemented in FogBugz.
The very first release is presented here. Watch out, though, this is an Extreme Alpha Release, so it holds absolutely no guarantees. Do not use for serious needs. Do not expose to children. Most of the UI is non-existant, if you want to see what's really going on, you'll probably have to run Thunderbird with the -console command line option. You'll also be treated to a whole lot of debug output.