Build a simple drawbot using old Lego motors, an Arduino, and a Modkit MotoProto shield. You can then program your drawbot to draw using Modkit Micro or the Arduino IDE.
Projects from Make: Magazine
Simple Modkit Drawbot
A simple laser-cut (or hand-cut) drawbot using Lego gears, wheels, and motors, an Arduino board, and a Modkit MotoProto shield.