Determine the doneness of a steak
It works like this: You touch your thumb to your index, middle, ring, and pinky fingers, and the further you reach, the harder your muscle becomes. Apparently this should match up relatively well with rare, medium rare, medium, and well done steaks as you work your way from index to pinky.
What an absolutely brilliant idea (assuming it works). So simple, and yet so useful.
Wandering the Interwebs 