Physics Engines for Dummies
Here's an A+ reference/tutorial for anyone looking for a  "not for dummies" version of rigid body dynamics:http://www.digitalrune.com/Portals/0/Documents/A%20Unified%2...(Had to google for a fresh link; unfortunately this doesn't seem to be nearly as widely mirrored as I believe it deserves.)Things I liked about it:- The author continually explains, compares, & contrasts alternative approaches throughout.- It builds up a full actual system, including a lot of discussion of what other references may dismiss as mere software engineering.- The author starts with the fundamentals and goes from there, usually fairly thoroughly.