The Stanford Natural Language Processing Group

That model is fairly slow. Essentially, that model is trying to pull out all stops to maximize tagger accuracy. Speed consequently suffers due to choices like using 4th order bidirectional tag conditioning. It's nearly as accurate (96.97% accuracy vs. 97.32% on the standard WSJ22-24 test set) and is an order of magnitude faster. Compared to MXPOST, the Stanford POS Tagger with this model is both more accurate and considerably faster. It all depends, but on a 2008 nothing-special Intel server, it tags about 15000 words per second.