Thsrs (http://www.ironicsans.com/thsrs/) is an interesting site. It's a thesaurus with a rub; you give it a word and it finds synonyms for the word that are shorter in length. If you're trying to be concise for whatever reason, this is a way to find the words you need.

A cool/funny site would be to enter a block of text and use a site/algorithm like this to completely update in word that is in the block of text. Could be funny to see what results. It'd be an interesting mash-up anyway.