A. Sense Relations: Wordnet
"WordNet® is an on-line lexical reference system whose design is inspired by current psycholinguistic theories of human lexical memory. English nouns, verbs, adjectives and adverbs are organized into synonym sets, each representing one underlying lexical concept. Different relations link the synonym sets." It is a "thesaurus" on psycholinguistic principles developed by George A. Miller and others at Princeton. The on-line version takes words as input and returns synonyms, hypernyms, (if nouns) coordinate words (words with same hypernym); if verbs, it also returns troponyms (instead of hypernyms) and entailments.
The celebrated
Thinkmap (formerly Plumbdesign) Visual
Thesaurus is a gorgeous front end for Wordnet. It takes words as inputs and returns rotating figures of connected synonyms, which can themselves be clicked on to branch synonyms .... Read through the information screens.
Lexical FreeNet "This program allows you to search for relationships between words, concepts, and people. It is a combination thesaurus, rhyming dictionary, pun generator, and concept navigator." LFN enhances the associations linked to a word from the purely lexical WordNet base by adding databases of people, things-with-their-parts, rhyming words and other stuff. It allows you to search for related words across a set number of links, and it computes the relatedness of two words via the linking words in the WordNet.
Bernard Bou in Toulouse has put up a hyperbolic viewer for Wordnet; it is worth the small amount of study it requires.
B. Verb Semantics
The VerbNet project at Martha Palmer's website integrates Wordnet synsets with Berkeley frame semantics, semantic/thematic relations, selectional features and predicate argument structure. It groups verbs into classes, and the resulting rich taxonomy with almost 6000 verbs can be accessed at the Unified Verb Index. Each verb is linked to Wordnet and FrameNet online entries.
The Cognitive Computing Group at UIUC has put up a Semantic Role Labeling Demo which takes sentences as input and identifies the semantic roles cast by the verbs in the sentence alongside a PennTree proper bracketing of the sentence (Charniak parser).