ArduPilot

= a family of open source autopilots based on the Arduino open source computing platform.

URL = http://www.diydrones.com/notes/ArduPilot

Example

It consists of a choice of ArduPilot Mega (APM) electronics and a range of free software versions for different vehicles:

"APM 2 is a pro-quality IMU autopilot based on the Arduino Mega platform, which can turn any RC vehicle into a fully autonomous Unmanned Aerial (or Ground) Vehicle. Depending on which software you choose, it can fly fixed-wing aircraft, multicopters, helicopters, and control ground rovers and boats. It handles both autonomous stabilization and GPS navigation and allows fully scripted waypoint missions and camera control. It supports 8 RC channels, has four serial ports and features an all-in design.

You can buy APM 2 for $199 here." (http://www.diydrones.com/notes/ArduPilot)