Can you write a Naive Bayesian classifier in just an hour? Yes, you can!
At least, i think you can. And i recently walked some people through it.
Unfortunately, it's very difficult to walk you through in a half hour. I tried at LPW '07, but i think i may have glossed over a few too many details. My slides are available, though.
Eventually, i'll include notes and such, and improve the slideshow. Until then, i'll link to the Bayesian classifier i wrote in an hour or so, to prove that i could. It's written in Perl, is completely uncommented, and may not make sense unless you sat through my talk (or are already familiar with Bayesian classifiers), but it's here as a reference.
Also here are the files i used as a training set. The problem was "is this email work email or non-work email?"