I'll leave them out for the kitty sometimes too! I also will sometimes straighten out the crumpled packing paper, and pile it up on the floor... kitty goes NUTS over that! He'll climb inside to hide, and push on it so it crinkles. Then after a while he's bored and moves on.
I save the packing paper to re-use, and re-use as many boxes as I can for selling on the Classifieds, or mailing care packages. The ones I can't use I recycle.