I love PopFile. It uses Bayes to do most of the filtering, but at the same time it looks for odd letter combinations like V!A6RA to make sure they don't get past the bayes filter. It can also use magnets to get rid of spam with known strings you want to deal with.

The group that maintains POPfile are realistic about the advanatges and disadvantages of bayes and as Spamers develop new tecniques they also expand popfile. I'm not a develper for it, I just have had great success with it.