Physics Model Editors

Physics Model Editor - The first of the two. Comes with extensive docs, and the author will also help you out if you e-mail him.

PME was found at:
AMUG, America Online

Playsets - Originated on E-world. Although easier to use than Physics Model Editor, there are less values you can control. Playsets reminds me of those Face-tracing books where you can take different heads and draw them with different ears, eyes, mouths, etc.

MPE was found at:
AMUG, America Online, E-world