I know I have posted a bunch of these up already, but this one is with an older L293D shield for an arduino. Why do I care? Well remember when radio shack was closing a bunch of stores, they had a bunch of these shields going for a couple of bucks.
http://www.instructables.com/id/How-to-Make-Mini-CNC-2D-Plotter-Using-Scrap-DVD-Dr/