I've written about Wordle, a word cloud generator, before. I think it's a great tool, and one that students can be very engaged in using. Thanks to TechnologyInEd for tweeting this!
This word cloud gallery, from Governing Dynamo is a collection if Presidential images and word clouds made from each President's inaugural speeches. One activity that came to mind as I played with this would be to have students look at the word clouds of the speeches of a particular president or era and have them generate a list of issues they think were important at that time. Once they've come up with a list of issues to research, they could create presentations (using Prezi, Animoto, Glogster or any of about a thousand other tools!) to give to their classmates about what they have discovered. A much more engaging way to learn about, say, the presidency of William Henry Harrison, or the events immediately preceeding the Civfil War than to simply listen to a lecture.
A caution about Wordle: There is some inappropriate content on the site which students may come across. I would give the kids a link to a specific word cloud you want them to look at or to the cloud generator. I would not have them search it on their own.