Using the graphical programming language Processing and an Arduino microcontroller, Trevor Shannon built himself a software-based Etch-A-Sketch. The Arduino reads the input from two potentiometers and then through a serial connection, lines are produced on a computer screen. Over time, the lines disappear, just like a real Etch-A-Sketch. A simple, yet intuitive way of using the Arduino to build a project. Oh, and the knobs are made from an old iTunes gift card!
Want to give it a shot? Trevor has provided the code and schematics that you need to get started.