We love to play with boxes.
Most often they are made into cars and trains, or used to stash a big pile of toys and given to mommy or daddy as a 'present'!
We got an extra big box one day and kept it around.
It was prefect for hide and seek, but they also loved when I puled out the crayons, markers and pencils and let them go to it.
An easy (and FREE!) activity that re purposes something that could otherwise just be trash.
Plus I love art activities that are a little outside the box (no pun intended)... why just color on paper when you can color on a big box?