Exploring Electronics Tiny flashlights for little personalities... these are 9V battery powered lights, each put together in ~60 min using 3V standard LEDs and resistors, some hookup wire, a push-button switch, and electric tape, on a small solderless breadboard. Appeal? 3 yrs and up. Total cost of components? ~£1.20. Exposure to electronics for young children? Priceless.

http://mathscitech.org/articles/exploring-electronics