I've blogged about my duckfeet before. I've found a new training tool that will keep me aware of when I duck foot, and hopefully help me correct it.
I recently moved to clipless pedals on my bike. If you haven't tried clipless pedals, the important thing to know about this as related to my duck footedness is that to unclip from the pedal you simply twist your foot. This is a good thing as there are times when being able to quickly separate your foot from your pedal can keep you from crashing, when your foot has a tendency to twist one way on the downward stride and the other way on the upward swing however it becomes very easy to unclip accidentally. Apparently for me this happens most when pedaling quickly.
As I am a silver lining kind of guy, I will use this unfortunate fact to help me stop twisting my feet so much. I think it will improve my running form as well as my biking.