Wow, was it ever hot in Washington, DC! Like a steam sauna. Anyway, I had a nice time despite the heat and managed to see all the sites I was hoping to see.
The Paper Engineering: Fold, Pull, Pop and Turn exhibit at the National Museum of American History was fun, but small. I guess movable book art isn't something the average NMAH goer is that interested in. This Smithsonian Institution Libraries' exhibit had some wonderful examples of movable, pop-up, folding and multiple-construction books dating from 1540 to the present. There are photos of many of the books on the exhibit blog.
If you happen to be in DC, it's worth stopping in to see this exhibit. However, the small size makes a special trip impractical.