Last weekend I ported the Reverend bayesian classifier from Python to Ruby (thanks Jon for the original pointer to Reverend). What I didn't realise was that Lucas Carlson
was, simultaneously, working a similar library… ah well, there's a
good chance we'll roll my work into his more general classifier library.
Anyway for what it's worth my port, Bishop, is available for download and as a RubyGem. I anticipate at least one more release before deciding what to do with it.