KMODDL is a collection of mechanical models and related resources for teaching the principles of kinematics--the geometry of pure motion. The core of KMODDL is the Reuleaux Collection of Mechanisms and Machines, an important collection of 19th-century machine elements held by Cornell's Sibley School of Mechanical and Aerospace Engineering.
http://kmoddl.library.cornell.edu/collection-toc.php

In addition to the photographic animations, KMODDL contains a number of interactive simulators that represent kinematic motion abstractly. The simulators allow users to interact with a machine, pushing and pulling in unscripted ways, modifying it and observing the consequences. Users can modify link lengths, connect and disconnect bars, and remove or modify grounding points, thereby creating inversions. They can also erase a machine and build a different one from scratch. The simulations are linked from the pertinent model pages (under “resources”). You can also browse the simulations by selecting the “multimedia” link from the right sidebar on the KMODDL homepage, or search by key word or subject.

The KMODDL team is using rapid-prototyping technology to reproduce physical models as 3D “prints” from digital files. The replicas are captured as stereolithography (STL) files, which can be exported for 3D printing in thermoplastic layers on a rapid-prototyping fabricator.