I used the eggbeaters from my mountain bike on the road bike for a while. Good for shorter rides; hot-spots after about 90 minutes. I got the Crank Bros. Quattros for the road bike which have a wider platform and a three-hole cleat for mounting on road shoes. I think they work great.

A bonus is that my road bike is a cyclocross bike so I can use my mountain shoes on the same pedals after I cut away a little bit of rubber on the sole to clear the larger bearing of the Quattros.