I've used both LingPipe and Stanford's POS Tagger. The later is a state-of-the-art POS Tagger but, from my experience, it is too slow (although they do provide less accurate models, which are reasonably fast). Of course, it always depends on what you are trying to achieve, and there will always be a trade-off between speed and accuracy.
I've also once used an LBJ-based NER software and, although it was pretty accurate, the source code was a complete mess. Both LingPipe and Stanford's source is very clean and well documented.
You can also take a look at LTAG-spinal. I haven't used it yet, but from the algorithm description, and from the listed accuracy, it sure seems better than the alternatives you have so far.
Hope it helps.
