Nltk

NLTK:
* added interface to the Stanford POS Tagger
* updates to sem.Boxer, sem.drt.DRS
* allow unicode strings in grammars
* allow non-string features in classifiers
* modifications to HunposTagger
* issues with DRS printing
* fixed bigram collocation finder for window_size > 2
* doctest paths no longer presume unix-style pathname separators
* fixed issue with NLTK's tokenize module colliding with the Python tokenize module
* fixed issue with stemming Unicode strings
* changed ViterbiParser.nbest_parse to parse
* ChaSen and KNBC Japanese corpus readers
* preserve case in concordance display
* fixed bug in simplification of Brown tags
* a version of IBM Model 1 as described in Koehn 2010
* new class AlignedSent for aligned sentence data and evaluation metrics
* new nltk.util.set_proxy to allow easy configuration of HTTP proxy
* improvements to downloader user interface to catch URL and HTTP errors
* added CHILDES corpus reader
* created special exception hierarchy for Prover9 errors
* significant changes to the underlying code of the boxer interface
* path-based wordnet similarity metrics use a fake root node for verbs, following the Perl version
* added ability to handle multi-sentence discourses in Boxer
* added the 'english' Snowball stemmer
* simplifications and corrections of Earley Chart Parser rules
* several changes to the feature chart parsers for correct unification
* bugfixes: FreqDist.plot, FreqDist.max, NgramModel.entropy, CategorizedCorpusReader, DecisionTreeClassifier
* removal of Python >2.4 language features for 2.4 compatibility
* removal of deprecated functions and associated warnings
* added semantic domains to wordnet corpus reader
* changed wordnet similarity functions to include instance hyponyms
* updated to use latest version of Boxer

Data:
* JEITA Public Morphologically Tagged Corpus (in ChaSen format)
* KNB Annotated corpus of Japanese blog posts
* Fixed some minor bugs in alvey.fcfg, and added number of parse trees in alvey_sentences.txt
* added more comtrans data

Documentation:
* minor fixes to documentation
* NLTK Japanese book (chapter 12) by Masato Hagiwara

NLTK-Contrib:
* Viethen and Dale referring expression algorithms

NLTK:
* many code and documentation cleanups
* Added port of Snowball stemmers
* Fixed loading of pickled tokenizers (issue 556)
* DecisionTreeClassifier now handles unknown features (issue 570)
* Added error messages to LogicParser
* Replaced max_models with end_size to prevent Mace from hanging
* Added interface to Boxer
* Added nltk.corpus.semcor to give access to SemCor 3.0 corpus (issue 530)
* Added support for integer- and float-valued features in maxent classifiers
* Permit NgramModels to be pickled
* Added Sourced Strings (see test/sourcedstring.doctest for details)
* Fixed bugs in with Good-Turing and Simple Good-Turing Estimation (issue 26)
* Add support for span tokenization, aka standoff annotation of segmentation (incl Punkt)
* allow unicode nodes in Tree.productions()
* Fixed WordNet's morphy to be consistent with the original implementation,
taking the shortest returned form instead of an arbitrary one (issues 427, 487)
* Fixed bug in MaxentClassifier
* Accepted bugfixes for YCOE corpus reader (issue 435)
* Added test to _cumulative_frequencies() to correctly handle the case when no arguments are supplied
* Added a TaggerI interface to the HunPos open-source tagger
* Return 0, not None, when no count is present for a lemma in WordNet
* fixed pretty-printing of unicode leaves
* More efficient calculation of the leftcorner relation for left corner parsers
* Added two functions for graph calculations: transitive closure and inversion.
* FreqDist.pop() and FreqDist.popitems() now invalidate the caches (issue 511)

Data:
* Added SemCor 3.0 corpus (Brown Corpus tagged with WordNet synsets)
* Added LanguageID corpus (trigram counts for 451 languages)
* Added grammar for a^n b^n c^n

NLTK-Contrib:
* minor updates

Thanks to the following contributors to 2.0b9:

Steven Bethard, Francis Bond, Dmitry Chichkov, Liang Dong, Dan Garrette,
Simon Greenhill, Bjorn Maeland, Rob Malouf, Joel Nothman, Jacob Perkins,
Alberto Planas, Alex Rudnick, Geoffrey Sampson, Kevin Scannell, Richard Sproat

NLTK:
* fixed copyright and license statements
* removed PyYAML, and added dependency to installers and download instructions
* updated to LogicParser, DRT (Dan Garrette)
* WordNet similarity metrics return None instead of -1 when
they fail to find a path (Steve Bethard)
* shortest_path_distance uses instance hypernyms (Jordan Boyd-Graber)
* clean_html improved (Bjorn Maeland)
* batch_parse, batch_interpret and batch_evaluate functions allow
grammar or grammar filename as argument
* more Portuguese examples (portuguese_en.doctest, examples/pt.py)

NLTK-Contrib:
* Aligner implementations (Christopher Crowner, Torsten Marek)
* ScriptTranscriber package (Richard Sproat and Kristy Hollingshead)

Book:
* updates for second printing, correcting errata
https://nltk.googlecode.com/svn/trunk/nltk/doc/book/errata.txt

Data:
* added Europarl sample, with 10 docs for each of 11 langs (Nitin Madnani)
* added SMULTRON sample corpus (Torsten Marek, Martin Volk)

NLTK:
* minor bugfixes and enhancements: data loader, inference package, FreqDist, Punkt
* added Portuguese example module, similar to nltk.book for English (examples/pt.py)
* added all_lemma_names() method to WordNet corpus reader
* added update() and __add__() extensions to FreqDist (enhances alignment with Python 3.0 counters)
* reimplemented clean_html
* added test-suite runner for automatic/manual regression testing

NLTK-Data:
* updated Punkt models for sentence segmentation
* added corpus of the works of Machado de Assis (Brazilian Portuguese)

Book:
* Added translation of preface into Portuguese, contributed by Tiago Tresoldi.

NLTK:
* minor fixes for Python 2.4 compatibility
* added words() method to XML corpus reader
* minor bugfixes and code clean-ups
* fixed downloader to put data in %APPDATA% on Windows

Data:
* Updated Punkt models
* Fixed utf8 encoding issues with UDHR and Stopwords Corpora
* Renamed CoNLL "cat" files to "esp" (different language)
* Added Alvey NLT feature-based grammar
* Added Polish PL196x corpus

NLTK:
* minor bugfixes (incl FreqDist, Python eggs)
* added reader for Europarl Corpora (contributed by Nitin Madnani)
* added reader for IPI PAN Polish Corpus (contributed by Konrad Goluchowski)
* fixed data.py so that it doesn't generate a warning for Windows Python 2.6

NLTK-Contrib:
* updated Praat reader (contributed by Margaret Mitchell)