Make your own photographic emulsion

If you're tired of paying The Man at Kodak or Fuji, why not try your hand at creating your own photographic emulsion? This silver-based mixture is intended to be coated on glass or film (yes, you get to play with a squeege). You'll need some sort of large-format camera that can accept a photographic plate (this technique will work wonderfully with a simple homemade pinhole camera as well).

The ingredient list reads like a toxic flavor of Jello: Gelatin, potassium bromide, potassium iodide, and silver nitrate. Remember that your emulsion is light-sensitive and you'll have to work in a darkroom with illumination from a safelight. If you're not adventurous enough to mix your own, you can buy premixed liquid emulsion from Photographers' Formulary.

Make a simple film emulsion (via a thread started by Paul Cotto at filmshooting.com)