Last year, for an IRP, one of my students did the experiment measuring the speed of light (and the wavelength of the waves) using marshmellows in a microwave. The video above (via Gizmodo) shows the pattern of the microwaves using some neon lights embedded in plastic. The video below, from MythBusters, shows superheated water in action; something I demo every time I make tea-water in the microwave.