In way of background for this post, I should explain that a camera obscura is a dark box (or room) with a hole in to that allows an image from outside to be projected into the camera (meaning, in the original sense, a "box"). The image is upside-down due to the pinhole lens effect. Also, the larger you make the hole the brighter but more fuzzy the image is. The camera obscura was the forerunner of both cinema and film cameras. Special rooms were constructed to allow paying audiences to view these projections as a form of entertainment.
With that background, I offer a link to a DIY camera obscura. This is a great project that improves on the original variety by incorporating a modern lens to allow bright AND sharp(er) images at the same time. I'm planning on making one of these with my kids during the summer holidays so they can view the morning sunrise in an interesting way.
(Hat tip: Make)