I'm right handed, but my left leg is stronger (and the left calf slightly bigger judging from how my boots fit ) so I like to power off with the left left first - same as Trigirl. So I always unclip the right first and don't unclip the left unless I actually have to get off the bike for some reason.

DH always gives me a safety lecture about it and we generally try to teach our new riders to unclip with the left foot, because if you're going to fall, you will fall towards the side that is still clipped in, which means falling into traffic if the left is still clipped in. One of many "Do as I say, not as I do" things - but habits are hard to break.