Since 1900, there have been 116 State of the Union addresses, given by 20 presidents, with some presidents giving two addresses a year. Studying their choice of words, over time, provides glimpses of change in American politics—"communism" fades, "terrorism" increases—and evidence that some things never change ("America" comes up steadily, of course. As does "I.").
For some reason the interactive won't load for me now (It did yesterday.), but there's also a PDF version that you can download. Although the PDF only goes back to 1989 Bush, so try for the interactive version first. It was an interesting one. Update: Works again.
Can you believe it? We made it through an entire SOTU without a single word cloud. Come to think of it, I can't even remember the last time I saw one. I almost feel cheated.