With a CD or DVD, a glue gun or thick glue, a sport drink bottle cap and a balloon you can create a CD hovercraft that will float on a table or other smooth surface. The air cushion is not lifting it very high, but it works quite well.
Due to the high bottle deposit fee I decided to print some for my students instead.
Warning: These are rather thin and for smaller balloons or the long rocket balloons. Increase the larger one by twenty percent to avoid trouble with the thin surfaces and to make it fit on larger balloons.
To avoid printing support structure you could create a angled seam, but it is not too difficult to print anyway.
Other improvements: decrease the hole diameter to throttle the output and increase performance and duration.
The animated GIF does not seem to work, try it here: http://blog.pixelgiraffe.com/wp-content/uploads/2014/03/gifhoverr4b.gif