I would like to have a kit for tinkering with motors. A kit could include: a 12 volt motor, a power supply, gears for it, belts, and mosfets for controlling it. It would be like the lego tecnic gear kits that everyone has played with. Instead of legos, a maker could just drill holes in a piece of wood, and use the parts in the kit to automate something.
It would be good to also have a tutorial for wiring the mosfet to the arduino.
I recently did a motor project and I had to go all over the place picking out the right mosfet and getting the gears I needed.