Visuwords (http://www.visuwords.com/) is an online graphical dictionary based on Princeton University’s WordNet (http://wordnet.princeton.edu/). Type in a word and it displays definitions, related terms, synonyms and antonyms as a diagram.
The colours show whether the words are nouns, verbs, adjectives or adverbs and the format of the lines joining them represent the type of link between words. A broken blue line, for example, represents “also see”. Move the cursor over a word to see a definition and double click on a node to expand it. This is a great tool if you are stuck for an alternative word and prefer a visual rather than textual approach to this type of search. It was suggested by one of my European contacts who was looking for a tool to help a colleague draft documents in English.