Bayesan Classifiers are one of the most powerful data mining tool. I use them everyday with very good results. I found out that having an accurate and rich training dataset is much more important than having a ultra-sophisticate classifier (such as SVM). Bayesan classifiers have a very simple math, are easy to implement, and provide very good results in almost all the situations.
Here you have a Naive implementation of Naive Bayesan Classifier.