CLAWS
http://www.comp.lancs.ac.uk/ucrel/claws/

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

TreeTagger online
http://cental.fltr.ucl.ac.be/~pat/tagger/

POS taggers list
http://www-nlp.stanford.edu/links/statnlp.html#Taggers

LingPipe
http://www.alias-i.com/lingpipe/

TnT
http://www.coli.uni-saarland.de/~thorsten/tnt/