The trick is that the Dock process is actually the one that controls Exposé. My Dock froze up while I had my windows laid out with Exposé, and when I killed it (by sshing in from another machine), it relaunched the dock, but the windows did not return to their normal size. I then discovered that I could click on the windows, bringing their application to the front, move them around, and even type in them. Clicking elements in the content of the window doesn't work, though, probably because there would have to be a mouse coordinate transformation that isn't happening.
To do this with one machine, open up Script Editor and enter the following script:
delay 3
tell application "Dock" to quit
Run the script, and during the three second delay, hit your Exposé key to lay out the windows. When the Dock quits, it will automatically relaunch, but you will now have mini-windows to play around with. You can restore your windows to normal size by hitting Exposé twice.
[robg adds: This is definitely nearly useless but interesting. On my machine, I couldn't do very much with the shrunken windows; no typing, just clicking and moving about...]

