DIY Drones is an excellent community site for amateur unmanned vehicle development. Using Arduino as a foundation they have created the ArduPilotMega universal autopilot autopilot hardware. It combines sophisticated IMU-based autopilot electronics with free Arduino-based autopilot software that can turn any RC vehicle into a fully-autonomous UAV. The software is open source and currently has three variations: Arduplane, for any fixed-wing aircraft, Arducopter, for any rotary-wing aircraft, and ArduRover, for any ground or water-based vehicle. The site has an active forum as well as a store where you can purchase all the ArduPilot Mega Controller, other Arduino hardware or complete Drone kits.