Check this out: Visuwords is an online graphical dictionary & thesaurus

Visuwords is an online graphical dictionary  that allows you to look up words to find their meanings and associations with other words and concepts, produce diagrams reminiscent of a neural net, and learn how words associate.

Visuwords uses Princeton University’s WordNet, an opensource database built by University students and language researchers. Combined with a visualization tool and user interface built from a combination of modern web technologies, Visuwords™ is available as a free resource to all patrons of the web.

Check out Visuwords here.