A pinhole camera is very easy to make yourself, although it can also be bought. Basically, it is a light-tight box with a tiny pinhole on one side (made with a needle) and photo paper or film on the other side (taped to the box). No lens, battery or automatic operation is used. A pinhole camera can be constructed from a can, container or tea can. The vessel used could also be a coffee pot, for instance.
Build your own : manuals
Some good quality designs for pinhole cameras can be found on the internet for free. Corbis has a collection of downloadable cut-outs available, all of them easy to build. Another cut-out model is the Czech Dirkon paper camera, that looks like a real camera.