Wikipedia
ArduCopter
ArduCopter is an open-source multicopter unmanned aerial vehicle platform created by the DIY Drones community based on the Arduino platform.
ArduCopter runs on the Pixhawk and Ardupilot Mega (APM 1 and APM 2) autopilot systems created by DIY Drones and sold by 3D Robotics.
The free software approach from ArduCopter is similar to that of the Paparazzi Project and PX4 autopilot where low cost and availability enables its hobbyist use in small remotely piloted aircraft such as micro air vehicles and miniature UAVs.
Original Unboxing ArduCopter by Chris Anderson by Jani Hirvinen and his team at DIYDrones was released on Aug 2010.