Water balloons -- Experiment to find the best balance of air/water for the effect you want. Take a long board with a series of nails in it. Put the board between the uprights from an old target stand, then loop rubber bands or strings over the nails to suspend the balloons.
Flour balloons -- use a turkey baster to blow a little flour into the balloon, then blow the balloon up the rest of the way. Best to use an air compressor to inflate flour balloons because getting the flour in your mouth is just nasty.
Plain old balloons. You can staple small ones by their knotted necks to a regular target stand (we play tic-tac-toe like this). Or get the long & skinny types, or a variety of shapes, and suspend them from a string between a couple of uprights -- they'll blow around a lot, even on a calm day, and provide a real challenge.
Full cans of cheap soda pop.
Any cheap & disposable container that will hold colored water. Milk jugs work well for the kids and have a high "wow" factor because there's so much liquid involved. Or try tiny little dixie cups, old shampoo bottles, just anything that'll hold water.
Rotten fruit and veggies -- ask your grocery store's produce manager for throwaways.
(Edited to add: cleaning up balloons is a pain in the backside, but you have to do it. If you aren't willing to spend way-too-dammuch time picking up the little rubber pieces, don't do balloons.)
pax
