Just a quick note that I have updated the MakerPlane website and uploaded a lot more free and open source avionics projects as well as a complete aircraft electrical system and avionics wiring schematic.
This might be of use to homebuilders out there. The aircraft electrical schematic also includes implementation of a few of the open source avionics already in the repository. Note that these are flying in lots of aircraft already! Check out the downloads page as an entry point into the open source repository. If anyone has any projects they would like to add, let me know!