The only pedals I've run across which seem to solve this problem for me are the "EZY Superior" pedals - they use a quick release attachment so you can swap which pedals are on the bike faster and easier than using a pedal wrench. I would own them except I prefer the Time ATAC pedals, and the "EZY Superior" are spd's. So basically it makes it a lot easier to swap between your clipless pedals (which you buy from them) or a straight platform pedal (which you also buy from them).

I don't like any of the other "solutions" -

1. Pedals like the Shimano A530's I find very, very annoying because I have to look down when I need to clip in. When do you clip in the most? When you're at a traffic light and should be keeping your head up looking at the traffic. Some people have said you just ride through the intersection with your foot on the platform side if you get the platform side, but the problem for me is that I wear stiff-soled mountain bike shoes which have hard plastic on the soles - and the platform side of the pedals is made out of shiny, slippery metal - I can't imagine that working well.

I did own a pair of a different version of these from Shimano, and always found the one-sided pedal thing to be really annoying...personally.

2. The 2 sided pedals with the large cage around them - good if you only need to ride half a mile to lunch or something, but not good for going with regular shoes for longer distances. I don't know - I mean, they're just not as comfortable, and you don't get as much shoe/pedal grip with them.

If I was using spd's I would use the EZY's and swap the pedals as needed.