WordNet® is a large lexical database, where words are grouped into sets of cognitive synonyms (synsets), each expressing a distinct concept. Synsets are interlinked by means of conceptual-semantic and lexical relations.
Global WordNet Association - The Global WordNet Association is a free, public and non-commercial organization that provides a platform for discussing, sharing and connecting wordnets for all languages in the world.
ImageNet - ImageNet is an image database organized according to the WordNet hierarchy (currently only the nouns), in which each node of the hierarchy is depicted by hundreds and thousands of images.
RiTa - an easy-to-use toolkit for experiments in natural language and generative literature. It includes text-generation via CFGs and Markov chains; taggers for syllables, phonemes, stress, POS. Rita also provides a Java-API for WordNet and morphology modules.
wn - a non-NLTK version of Python interface to WordNet.