After reading a couple of online articles about building your own mechanical camera stroboscope I decided I had to try it. Here are some photos of my build. Its a pretty simple affair. A toy motor turns a disk, with a hole in it, in front of a camera. Shine a lot of light on your subject, preferably with a dark background, set the camera for a one or two second exposure and take a picture. Hopefully you will get a strobed effect. 
Here are two websites that explain in detail the process of building the strobe so I won't be going into any real detail on my build.
http://makeprojects.com/Project/Stroboscope/313/1
http://people.rit.edu/andpph/text-stroboscope.html

The first photo is a bouncing ping pong ball illuminated only with a led flashlight with a two second exposure.
The second photo is a photo of a yo-yo
The third photo shows my disk which is the bottom of a plastic DVD container. I cut a slot in the disk as described in the above links. I attached the disk with part of a toy fan to the motor shaft. The red lens cover is just a plastic bottle with both ends cut off. I darkened the inside of it with a sharpie. Its purpose is just to cut down on extraneous light. 
The next photos show my build. Basically a battery wired to a toggle switch wired to a toy motor.
Every thing is bolted to a piece of plywood which is bolted to a plastic bucket/basket which serves as a  cheap tripod.
The other photos are some quick examples: juggling, a girl dropping her arms, a flashing party light, a Monkey Fist knot., dropping my hand, another party light swirled in PhotoScape.
The links above provide a lot of good information on how to build the machine and how to use it.