There's a show (foreign to me so I find out a bit late) called Dara Briain's Science Club. It's interesting to say the least.
So anyway on one episode they show how to calculate the speed of light using cheese on bread in a micowave oven. The how is by disabling the turntable, cooking for a short time and measuring the distance between hot spots where the cheese started to melt. That goes into an equation... I guess based on interference (at least that's what we used in physics class 1973) to get the wavelength which multiplied by the frequency got them within 7% of the actual value.
That using a pocket scale to measure distance between 2 melt spots in cheese as the experiment data gathering is just pure brilliance to me.