Cannot comment on folding pedals, but I do use MKS pedals. They have a quick release coupler similar to that used in an air hose coupling. I think mine are called the AR2 and are a single sided platform pedal. I have power grip straps installed and the combo has been wonderful.

Here is a pic of my Bike-Friday with one of the MKS pedals removed and sitting on the floor next to it. The female coupling which remains attached to the crank arm is also visable in this pic.

http://s164.photobucket.com/albums/u...Picture120.jpg

MKS also has a double sided platform and a clipless pedal also with the QR option. The downside to the clipless pedal is it uses a spd look alike cleat that is not compatible with shimano spd.

http://www.thorusa.com/dahon/accesso....htm#promenade