Check out visuwords at http://www.visuwords.com/
This is an online graphical dictionary and thesaurus AND MORE!
I used this with my Latin club to show them English words with Latin roots.
Type in the word "maternal" for example and then watch all the connections.
This is great for a research tool. We used it to find information on mythology.
Type in Zeus. Hover over the word for a description.
Then double click on the connecting element "Greek deity" and watch it POP. The students love this.
You can click and drag the circles and watch the "design" move.
I can see lots of uses for this tool in the classroom. The students ASK to use this!