If you are unfamiliar with the concept, you take a light-tight box, poke it with a teeny hole, place film inside (while in a darkroom or blackbag), and then remove the hole (lens) cover and voila! Photos in focus. Check out this site over at Merrill Photo for instructions on how to make your own pinhole camera from Altoids tins.
If you got the bug to hack stuff or build things from scratch, check out the folks over at Make. You’ll find a posting about the Altoids pinhole cameras there but also wild things you can make like this or this.
Check out this site for links to a variety of homespun pinhole cameras out of some very unique items like a can of spam or this: