I am staring work on a visual thesaurus.
I will use http://kenneth.kufluk.com/google/js-mindmap/ to handle the JavaScript side of things and use ajax to load the thesaurus entries if anyone would like to help on this project contact me at webmaster@spiders-design.co.uk.
Updates will be posted later.
check out progress by going to http://spiders-design.co.uk/process2.php?word= and put your word at the end