Over at FeelingNegative.com, we've started a DIY Large Format Camera project and our first step was to make a pinhole camera that exposes paper negatives.
I spent last weekend building 3 different cameras for myself and with the kids, and we all took a few shots and made prints. The cameras turned out good and the photos aren't bad either.
If you're not already following the project and you're interested in trying this type of thing, head over there and see how I made my first pinhole camera (it's a step-by-step DIY kind of thing).
[UPDATE 04-12-2010] You can also view a video I put together on developing paper negatives from these types of cameras.