This is great. If you don't know what a tag cloud is there's a primer at the top of the page. And while this loads to Bush, there's a slider at the top of the page that takes the concept all the way back to Washington.
US Presidential Speeches Tag Cloud - Chirag Mehta : chir.ag
Can you guess what two words are Bush's most used? I'll give you three guesses and the first two don't count.