I know this is a little goofy, but we had so much fun the other evening, sitting down together on a blanket with a package of coffee filters and seeing how high we could build towers out of the filters.
They really are fun to stack. The fluffier you make them, the easier it is to make them pile high. At one point, we had a tower as tall as little G (much to her delight).
Then of course, there is knocking them down and reveling in the floating coffee filters like snowfall- fun!