Another cool post from hackaday, about the process of hacking a cheap toy RC quadcopter so that it can be controlled by arduino.. It looks like its this toy quadcopter from > hobbyking.
Building your own quadcopter is an expensive and delicate ordeal. Only after you navigate a slew of different project builds do you feel confident enough to start buying parts, and the investment may not be worth your effort if your goal is to jump right into some hacking. Fortunately, [Dzl] has a shortcut for us; he reverse engineered the communication protocol for a cheap toy quadcopter to work with an Arduino.
He cracked open the accompanying control handset to discover which transceiver it used, then found the relevant datasheet and worked out all the pin configuration involved in the SPI communication. Flying data is transmitted as 8 byte packets sent every 20 mS, controlling the throttle, yaw, pitch and roll.
DLZ has also created an arduino library for this which can be downloaded from his dropbox