For another project I'm working on I needed a way to cut many, many circles. Since the circle-cutting jig isn't necessarily tied to the other project I decided to write it up separately.
I used a bandsaw for this jig, but it could also be used for a disc sander, or even a table saw. (See also the amazing Dan Rojas' video
on cutting circles with a table saw.)
The jig costs essentially nothing, is very easy and fun to use, and best of all opens ip a whole new level of capability to use on your future projects! For an example of the kinds of possibilities this opens up, see the disc sander pics on the last step.
(P.S. I just opened the licence up to full-fledged public domain so you can rest easy using it for your shcool / techshop / or whatever you want.)