I ran into these while Stumbling. Thought they were neat.

First the cool chop. At least I thought it was cool.
http://farm1.static.flickr.com/146/422520977_055eee8cf3.jpg?v=0 (flickr so you have to click it to see it)


Next is a pic that quickly describes perspective and vanishing point (a bit anyway).

The cool chop from Tofu's link above


as far as the second one - I wouldn't call it correct perspective and vanishing points, looks more like a numbers exercise.

as always, i have a great tutorial on perspective and vanishing points, but it's 1gb, so you cant have it