If you find Bayesian filters useful, here are two interesting open source packages I found, thanks to Stuart Langridge.

Reverend is a general Bayesian classifier written in Python.  If you are tired of hacking SpamBayes, you might want to give Reverend a try.

Orange is a component-based data mining software with a nice bayesian library inside it.  It is implemented in C++, but comes with Python binding and something called Orange Widgets.