Here’s a creative example of an Arduino project. It’s an Arduino painting machine. It’s an Arduino Due hooked up to a Samsung Galaxy Note tablet. You paint you picture on the Galaxy, and send it to ‘print’ to the printing machine. It’s a pretty impressive piece of kit and Kris Temmerman details how you can make your own, with schematics and code, at his website.
It uses 3 stepper motors for X-Y travel and brush height. He has also optimised the base code to use timestamps instead of Sleep().