Inspired by a project file sent to me by Chris Priddy (thanks again!) this tutorial shows the creation of a basic tank tread and then an easy way to animate it using expresso. Lastly I show how to tie everything together and set up user data to control the whole rig with one track of animation.
P.S. if you already know how to model the tread segment and want to skip to the animating, jump to 3:43