I've been using the Shimano PD-M424, it has a double-sided SPD pedal inside a rounded plastic platform. I tried the Campus style pedals and didn't like the way the SPD side worked.
http://www.nashbar.com/profile.cfm?s...TOKEN=71227240
You can use these with or without cleats and if you bump into something while the bike is folded they shouldn't do much damage since there are no sharp edges.