Make a cheap DIY electroscope, an instrument used for static electricty experiments, with items you would find around your home: A glass jar, two little pieces of aluminum foil, 14 gage copper wire, black electrical tape, a plastic lid to a container, a small plastic tube (or straw), and a hot glue gun (optional). This video shows you how to construct it, and how to test it.
An electroscope shows you how much an object is electrically charged. That is, it shows how much excess negative or positive charge an object has. An easy way to charge an object is to use the triboelectric effect, where you rub two objects together, such as a balloon and your hair. The objects must be as far apart in the triboelectric series, one on the negative side (rubber balloon) and one on the positive side (your hair.)