The use of multiple compasses to map and visualize magnetic fields is well-known. The magnetic field exerts a torque on the compasses aligning them along the lines of force. Some science museums show the field of a magnet using a table with many compasses in a closely packed arrangement. However, the very interesting interactions that occur between the compasses themselves are frequently neglected. In this paper we describe demonstrations, using arrays of compasses, that show these interactions and model magnetic domains in ferromagnetic materials.