A pinhole camera is a simple camera without a glass lens. They can be made out of almost anything, instructions are available all over the web along with how to calculate the exposure time. Corbis has posted several extremely cool PRINTABLE pinhole cameras -- for free.
Here is a lovely image shot with a pinhole camera. I would be proud of this image from any camera, its even more impressive when you consider the simplicity of the equipment. I am going to get going on this project and try it out.
"Mamya 645 6x4.5 camera fitted with homemade pinhole, diameter 0.35 mm, F 160, B&W negative Ilford FP4Plus 125 ISO, exposure time 3 sec, EV 14"