My friend Emma first introduced me to this exercise. It's a really great boarding challenge that helps train you to come up with entertaining ideas quickly.
The idea is you start with a random photo (Flickr is a good source for these) and you treat it like the first shot of a short film. Then you figure out what happens next, and board the next five shots; not the next five panels, but the next five unique shots. In the end you should have six drawings (including your starting image).
We're doing this exercise with our story trainees at the studio right now and i realized i'd never posted any of these here. This is one i did using this photo as a starting point.
(TECHNICALLY i cheated; i added a second panel for my first shot, so i've got seven drawings here)