I would recommend this resource because it is readily available and it is a referential named entity recognizer for English language with state-of-the-art (or nearly) results.
it's easy to use and good results.
the trained sets are pretty accurate and saves a lot of time.
GNU General Public License, well-documented.
This is the most well documented, easy to use NER that implements a CRF classifier! In case you get stuck, there is a very active user forum to get help! :-)
This is good resource, specially for the NLP community. I myself used it for some data mining experiments.
It was quite easy to use and has state of the art performance.