Visuwords

 Visuwords is an online graphical dictionary and thesaurus.  All that you do to use it is type in a word at the top.

A web pops up with the word and synonyms and antonyms.  It is really neat because it shows the relationship between the words and the other words that show up in the web by

This tool is probably more useful for upper grades, but can still be applicable with younger students and basic parts of speech.