Easy fun is often the best fun!
Paper Grocery Bags
Fill the Paper Bags full of scrunched up newspaper until the bags are about 3/4 full, then fold over the bag forming it into a block shape and tape it closed.
Have children stack the blocks and knock them down!
Build Gross Motor Skills and get out some energy! Especially perfect for rainy/snowy days.
You can also make smaller blocks out of smaller paper bags, and color the blocks (or even paint them if you really want to go wild!)