A variety of small found objects (shells, acorns, corks, bottle caps, etc.), poster board and a ruler to draw 6, 9, 12, or 15 squares
Create two game boards by drawing squares on the poster board. Place sets of the same objects in the squares, in a row. Give your child the second game board and identical items and ask him/her to duplicate what you did. Take turns creating sets and classifying objects
With younger children, start with six squares (two sets of three objects). Take turns, or take the lead from your child as he/she might invent new games using the objects.