Ardupilot

Forums
https://groups.google.com/forum/#!forum/drones-discuss Diy drones forum
 * http://ardupilot.org Developer driven, over 130 individuals committing code, one full time Intel employee.
 * https://www.dronecode.org/dronecode-software-platform Merging with diydrones.
 * http://copter.ardupilot.com/wiki/apm25board_overview/ APM, diydrones wiki
 * See Gentlenav, Gentlenav forums for the matrix pilot

VTOL of X8 plane
It was outfitted with the PX4 flightstack too which I recently added the VTOL_TAKEOFF and VTOL_LAND support. The maiden flight of the DeltaQuad was a succes. It slightly overshot it's landing site due to a miscalibration of the airspeed sensor (it was flying faster then measured). Still it made for a very smooth flight. In the next few weeks we will start payload and endurance testing, based on the current data it looks like it could carry a 1-2 kg payload for a distance of around 80km.
 * http://diydrones.com/profiles/blogs/deltaquad-vtol-autonomous-maiden-flight
 * https://github.com/sanderux
 * http://px4.io/portfolio/quadranger-vtol/

Pixhawk
http://diydrones.com/forum/topics/pixracer-with-ardupilot,  http://www.auav.co/product-p/xr-v1.htm

Python
Script copter with python http://python.dronekit.io/guide/copter/guided_mode.html
 * https://gitter.im/dronekit/dronekit-python links from diydrones google groups

IR lock landing
https://groups.google.com/forum/m/#!topic/drones-discuss/jjS8J7nLte0,  https://github.com/bstone04/ardupilot,
 * http://irlock.com/collections/ir-lock-pixy/products/ir-lock-filtered-pixy, Simple and accurate target tracking hardware for Drones & DIY Robotics. Works in bright sunlight and even complete darkness. https://www.kickstarter.com/projects/258964655/ir-lock-infrared-target-tracking-for-drones-and-di

Linux implementation

 * http://sasecurity.wikia.com/wiki/Erlerobotics.com
 * http://bbbmini.com/ arducopter on beaglebone
 * http://www.emlid.com/ Arducopter on Rasberry

China clone
arducopter chine clones

Witespy
Witespy arduclone small form factor. Pixhawk IMU is to larger for nano drones.

muav.in
http://diydrones.com/forum/topics/current-architecture-of-drone-autopilots-is-wrong-drone-hardware Suggestion to offload functions to separate processors and not use RTOS. www.muav.in drones,  http://diydrones.com/profiles/blogs/simple-distributed-flight-controller-network

Links
http://dronesarefun.com/VisionSystems.html