Oh, I just switched to clipless a few weeks ago. The first and only time I fell (the day I installed my new pedals) I unclipped on the left, came to a stop, and leaned left. However, just like with you, my foot had gotten itself at least partially clipped back in. I panicked, couldn't get unclipped in time, and fell down. Since then, I have been letting my left leg hang straight down in advance of stopping. That way I know it won't accidentally clip back in. Also, with it stretched all the way down, I kinda reach that foot toward the ground as I come to a stop and this helps me lean the right way (towards the unclipped foot). Riding clipless still makes me a little nervous, and I still think I'll fall again, but I'm getting the hang of it - you will too!

Clipping in fast again after stopping for a red light or stop sign is also a bit of a challenge. I ride with groups that push me to my limits, so if I don't clip in fast enough I risk getting dropped (or having to bust my a** to catch the group). I kinda look down during the stop to see how my pedal is positioned so I know whether I need to turn it over or not when I get started. That way I can clip in pretty fast. When I forget to do that, or let the pedal spins as I trip to position it, I lose precious time!