Last week while traveling, I stopped at a Zany Brainy store and saw that they had a blimp for sale. It's called Airship Earth, and it's a great big balloon with a map of the Earth on it, and two propellers hanging from the bottom. You blow up the balloon with helium, put batteries in it, and voila, you have a radio control indoor blimp.
I'd seen these things for sale in Sharper Image catalogs for $60-$75. At Zany Brainy it was on clearance for $15. What a deal!