My boys love all things Batman. Yesterday I stacked a few pieces of scrap paper, cut them into the shape of a bat (roughly...), and hid them around the house (there were 12). It look me 3 minutes to set up, but took them almost 30 minutes start to finish! Fun for them, easy free time for me!
I numbered them and had the kids put them in order when they were done. Then they extended the game by hiding them from each other AND are asking me to do the same thing this afternoon. Free and easy? Sure!