We recently bought a new room sized rug to go in our living room since the floor is covered with tile. It came rolled up on a giant cardboard tube. I knew this tube held endless fun possibilities, and here is some of the fun it has brought to our humble abode.
We set it up against the couch, and raced cars down the tube. Here are some pictures of the fun:
This amount of fun makes you want to buy the rug just to get the tube! But in the case that you don't really need a rug, I'm sure you could try the same thing using wrapping paper rolls, or paper towel rolls. You could even tape some together to make your tube longer!