NLP常用开源/免费工具

我发现大家经常询问一些类似的问题，例如stemmer，tagger等。
不如我们一起整理一下，置底造福大家吧。
对一些常见的NLP任务的开源/免费工具，
请大家用RE文模式按照分类提供名称和URL。

*Computational Linguistics Toolbox
   CLT http://complingone.georgetown.edu/~linguist/compling.html
   GATE http://gate.ac.uk/
   Natural Language Toolkit(NLTK) http://nltk.org
   MALLET http://mallet.cs.umass.edu/index.php/Main_Page


*English Stemmer
   Snowball http://snowball.tartarus.org/


*English POS Tagger
   Stanford POS Tagger http://nlp.stanford.edu/software/tagger.shtml
   TreeTagger http://www.ims.uni-stuttgart.de/projekte/corplex/TreeTagger/


*English Parser
   Stanford Parser http://nlp.stanford.edu/software/lex-parser.shtml


*English Keyphrase Extractor
   KEA http://www.nzdl.org/Kea/index_old.html
  

*English Name Entity Recognizer
   Stanford NER http://nlp.stanford.edu/software/CRF-NER.shtml


*Chinese Word Segmentator
   中科院ICTCLAS http://www.nlp.org.cn/project/project.php?proj_id=6
   Stanford Word Segmenter http://nlp.stanford.edu/software/segmenter.shtml


*Topic Modeling Tools
   Matlab http://psiexp.ss.uci.edu/research/programs_data/toolbox.htm


*Machine Learning Methods
   CRF++ http://crfpp.sourceforge.net/
   LIBSVM http://www.csie.ntu.edu.tw/~cjlin/libsvm/


*Search Engines
   Lucene http://lucene.apache.org/
   中科院FirteX http://www.firtex.org/


*Data Mining Toolbox
   Weka http://www.cs.waikato.ac.nz/ml/weka/