DIY: Making Your Own Tilt-Shift Lenses
It's pretty uncommon that you'll actually need to use a tilt-shift lens for anything. You'll see them used in architecture photography as a way to capture the images of large buildings, but more commonly they're used in miniature photography. Tilt-shift lenses keep the focus sharp on one part of an image while letting the other parts go blurry - it's a great way to simulate distances that might not actually be there.
You can pick up a tilt-shift lens from a variety of manufacturers, but it won't come anywhere near cheap. At minimum you'll have to spend a few hundred dollars. On the other hand, if you build your own you're looking at an investment of around $50.
A great guide from cow.mooh.org not only shows you how to build a few different types of lenses, but explains the uses of each. Certain lenses may not work as well with certain cameras, though a medium-format lens seems to work nicely with all of them.
You can even get some tips on shooting photos and video with your self-made tilt-shift lens, and some insight into less traditional uses.