If you're a shutterbug who loves a good DIY project, there are some fun kits out there that allow you to assemble your very own camera from the bottom up. The following kits use 35mm film and are all relatively inexpensive.
Papercraft Leica Pinhole Camera (Free) - London-based designer and photographer Matthew Nicholson created this fully functional papercraft Leica pinhole camera, which uses 35mm film. His personal site also features downloadable paper templates for a fancy wristwatch and blazer. The template for his Leica pinhole camera is not currently available on his site but says we can expect it soon.
DIY Pinhole Camera ($25) - This pinhole camera kit (from the popular photography site Photojojo) not only comes with a DIY camera you put together yourself, but also comes with a sunprint kit. The kit comes in plastic pieces that you snap together to make a functioning pinhole camera. The sunprint kit captures shadows using light sensitive paper when put out in the sun.
Twin Lens Reflex Camera ($39) - DIY Webstore the MakerShed sells this twin lens reflex camera kit straight from Japan. The unique camera has two lenses—one to compose and focus the shot and the other to take the actual picture. The viewfinder is positioned at the top so you take pictures by looking down on the camera, giving you a unique perspective.