It’s been a really long time since I’ve done any work on my quad-rotor flying thing. I got re-inspired after playing around with a new-ish PIC chip called a Propeller, made by Parallax. It runs 8 hardware threads at 20 MIPS each, meaning you can do really sensitive timing code without interrupts, but do lots of other useful things at the same time.
This is a perfect chip for a project that needs to listen to a remote control, take gyro readings, and move servos all at the same time. It does lots of other cool stuff too, like generate video, which is incredibly useful when debugging. 
So I got a 3-axis accelerometer, a dual-axis gyro, a 12-bit ADC, and stuck them together with a Kalman filter and some PIDs. Mix gently and let simmer for a month or so, and voila!
I present flying object #2 (WMV, 48mb), or on YouTube
The software is currently keeping it (somewhat) stable, but within a few more iterations on the software I hope to have it self-levelling.