Tilt Shift Lenses are cool. They are those lenses that allow you to take those miniature looking photographs.
I dare you to get a real one; Both Nikon and Canon models are so pricey that you have to give a kidney to afford them. (OK, maybe just a pinky). But we have some good news. Bhautik Joshi (the inventor of the weirdly named plunger cam) and John Swierzbin (who is a DIY lens master) came up with an extensive tutorial about building your own tilt shift lenses.
Actually this is definitely the best tilt shift tut that I have ever seen and it covers the theory (with very clear diagrams), how to fake the tilt-shift effect, and an explanation on how to build one.
They also share tutorials for four DIYed tilt shift lenses: Bendycam, Plugercam Classic, Plungercam mini and Plugercam 2. Each is a great afternoon project to build. And only cost about $10. (you can make about 220 DIY lenses for the price of a commercial one ;)
The amazing guide can be found here.
The time lapse video below demonstrates the full extent of the plunger tilt-shift effect.