Also in my past, my daughter and I sat down, and made a flashlight out of lemons (although any citric acid source can be used). Take a piece of copper, a piece of zinc and insert it into the lemon. The copper side is your positive and the zinc is your negative, hook it up to your bulb. You may have to parallel the circuit with other lemons to obtain more voltage, but this could be a fun/all-else-fails source of light.