If you frequent RCGroups, you'll have encountered the wildly entertaining (and illuminating) near-daily posts
of "Jack Crossfire", who's been chronicling his struggles in getting a very ambitious low-cost heli autopilot working. He has a site
where you can learn more about the "Vicacopter", project and check out his source code
. (You'll find his real name, which is no secret, in the code, and also how to contact him directly.) If you want to learn more about anything from Kalman filters to neural networks as they apply to aircraft control, his code is instructive, if a bit dense for mere mortals.
You can also see him interviewed in our PBS segment
. It's fascinating to watch an ace engineer wrestle with some of the same issues that we find difficult, and because he's so focused on DIY and low-cost solutions, it's very appropriate for this site.