There are many amazing hacks and techniques featured here, but some are likely out of reach for the average person (though a local hackerspace can help elevate those skills). On the other hand, this CNC dual arm Plotter was built using common hand tools, including drill bits, a wood saw, and a soldering iron. Making it even more accessible, the main arm is made from four plastic rulers that would normally be destined for a middle school somewhere.
Electronics-wise, an Arduino Uno is used to drive two stepper motors, which through a clever geometric configuration can move a pen on the end of the resulting parallelogram all over a piece of paper. A simple servo lifts the pen off the paper when needed.
Though quite interesting for any Maker, given the trigonometry going on to produce plots with this device, it could also make an excellent school project!