A friend of mine recently turned me on to the incredible resource Kinematic Models for Design Digital Library, or KMODDL, run by the Library at Cornell University. The site has many, many models of different mechanical movements, designs, gears- and enough brassy bits and whatchamajigs to keep your boiler steamed for awhile. To top it all off, many of the designs have not only movies, but downloadable CAD files; which so far I have used on a laser cutter (brag) and a 3D printer (BRAG! BRAG!).

Even if you aren't using KMODDL to, you know, make stuff...It's still awful purdy.

(shown above is Darts Chamber Wheel Mechanism- click for the amazing video)