Here are a couple of pointers for the Part of Speech Tagger. The first one it is the one I am using for my project. It was developed by the University of Stuttgart and it has the advantage to support multiple languages as it is based on a probabilistic criteria.

http://www.ims.uni-stuttgart.de/projekte/corplex/TreeTagger/DecisionTreeTagger.html

The following, from the University of Edinburgh is just for the English language. The page has also some good pointers to some literature on the subject:

http://www.ltg.ed.ac.uk/software/pos/

Here is a general overview on the subject:

http://www.georgetown.edu/faculty/ballc/ling361/tagging_overview.html

Tags: tagging, text data mining