2 microwave-safe glasses
1 incandescent light bulb (60 watts works well)
1 microwave oven
Directions: Fill one glass with water. Put the light bulb in the other glass so it doesn't roll around. Put both glasses in the microwave. Turn the microwave on for three seconds (use the low-power setting if it has one).
Watch: If your microwave has a turntable, you will see the light bulb glow and dim as it travels. If your microwave doesn't have a turntable, repeat the experiment several times, moving the light bulb to different spots. Be careful, the light bulb gets hot! And don't run the microwave longer than five seconds at a time.
The science: Light bulbs glow when electrons speed across a thin metal wire called a filament, heating it to several thousand degrees. In this experiment, you harnessed the energy of the microwave radiation generated by your microwave oven.
It sounds interesting enough. But I can't help thinking "Holy Cow! Someone's not going to follow the instruction and will blow up his/her microwave oven!" Then again, a spark in a microwave oven is, in itself, a fun physics experiment. :)