It's hard to get involved in the world of electric motors without learning about Electronic Speed Control (ESC), circuit designs frequently used in remote control systems. While more commonly associated with remote-operated aircraft, cars, and submarines, ESC systems have a larger-scale use in personal electric transportation - in particular electric skateboards and longboards.
Benjamin Vedder's open-source ESC circuit, Vedder's Speed Control (VESC), is a popular design in such projects, and John Pascoe is currently working on an Arduino-based wireless controller add-on which allows a Nintendo Wii Nunchuck to interface with a VESC circuit in order to provide fine-grained control of the connected motors.
The project isn't as straightforward as it seems. Although there's been plenty of work done on interfacing the Nunchuck with an Arduino, getting the Arduino to talk to the VESC board is slightly trickier: as the controller has to emulate an existing wireless NRF radio system, it needs to calculate an additional cyclic redundancy check (CRC) value. At present, John's design is functional but requires a modified VESC firmware; John has promised to provide full code when he has a way to make it work with unmodified VESC boards.
All you need is an Arduino, Nunchuck, 2 RF24 modules (You can get 10 for like 3-4$ on eBay). I also used a disassembled usb battery for power (Thinking of swapping it with LiPo so I can fit it in the Nunchuck). I'll post code later when I make it work with unmodified VESC firmware and maybe a small guide.