Recommendations for clipless pedals that can be used with regular shoes
I've been using Shimano A530 pedals for that purpose. Mountain SPD-compatible clip on one side, with a nice wide flat platform on the other.

I've also used the old Shimano M324 pedals, but prefer the slightly lighter weight and lower profile of the A530s.

Note that other foot retention systems, such as PowerGrips and the like, will work with all shoes (such as winter boots) and many existing platform pedals.