Check out the following links for word webs.
Princeton Wordnet
Wordnet.Princeton.edu
Thinkmap Visual Thesaurus
http://www.visualthesaurus.com/
The University of Alabama Libraries Scout
http://scout.lib.ua.edu/
Snappy Words: Free Online Visual Dictionary
http://www.snappywords.com/
Visuwords: online graphical dictionary.
http://www.visuwords.com