I've seen this link crop up in several places over the last week or two, but you never know who's seen it or not. So...
Chirag Mehta has generated tagclouds for Presidential documents/speeches (State of the Union Addresses and others), going back to 1776, and offered them for your perusal. (Usability note: I found it a lot easier to use the arrow keys to move the slider back and forth one at a time, but didn't figure out that I could use them until the fourth time I visited the site...)
It's an incredibly cool project, and what we're doing over at the CCCOA is obviously related, although our output is structured in different ways. Although we've got other things occupying our front burners at the moment, this site has definitely got me thinking about how we might build on our work there. More broadly, and perhaps relevantly, it's also got me thinking about how visualizations of trends in language usage might be folded in to some of the work we do in our field.
That's all.
Makes me think, as well, how cliches get circulated. "Freedom" and "Families" are to presidential speeches what "audience" and "purpose" are to writing pedagogy. Thing is: the presidential one seems to have more variety over time than the pedagogy one...