When Michael asked if we could make a camera, my initial reaction was 'no'. Then I suddenly thought 'pin-hole camera'. A milk-carton and a piece of grease-proof paper later, we had a working pin-hole camera. The only problem was that, with such a small aperture, it was virtually useless.
After a bit more thought, we used a magnifying glass, a box, some more grease-proof paper, some duct-tape, and a parka (as a hood), to make this view camera. It was much more successful, and we spent quite a while playing with it. Michael was really taken with it.
File under 'things to build with bored kids'.