Gary Teachout has put together an interesting robot that uses a Motorola 68HC11 as a brain and K’NEX for the structure. It has some smarts built into it, this includes a fight or flight reaction!

"ERC is a small computer, a few motors, some cardboard, and a bunch of K’NEX. For a long time it was a mobile robot, with differential drive, and I used it for many navigation experiments. It has an oscillating scan platform with two seven zone, convergent mode, infrared, range finders. Seven IR emitters mounted behind the upper lens (pocket magnifier), produce beams that converge with the field of view of a detector (behind the lower lens), at different distances from about nine inches away, to nine feet away. ERC divides this 360 degree view into 32 directions, and for each gets a distance of one to seven, or beyond range."