Clothespin Math on a clothes hanger! LOVE this. Easy to make, and self explanatory. I'm thinking a wire clothes hanger would work better, so the clothes pins are easy to slide back and forth (almost like an abacus).
For when they get older and start learning fractions. Learn fractions in a creative way by making these fraction flowers out of paper plates- includes a set of printable fraction circles. This makes learning math fun!