Balloons

Harris Teeter is the best grocery store. Not because of its prices or produce, but because they give the kids helium balloons after the shopping is done (bonus, if you are encumbered with children, they offer to take your groceries out to your car).

Anyhow, when the balloons have just a little life in them, when they just barely hover over the floor, I cut the strings off. The kids love playing with them in this state. They just spent 20 minutes throwing them up, letting them drift slowly back to their hands, and hitting them back up in the air. There was a minor fight over whose color belonged to whom, but other than that it was great entertainment.