I saw this on a kids science program and have been dying to try it. The host openned a baby diaper and a bunch of of the 'diaper sand' poured out. He explained that it was called 'polyacrylate' and could absorb thousands of times its own weight in water. He put whatever fell out of the diaper into a clear 2qt softdrink pitcher. He then poured in 2qts of colored water and stirred. He stopped stirring and talked about the uses of polyacrylate. After a bit he picked up the pitcher and turned it upside down over one of the kid's head. The liquid had turned into a gelatin that would not come out of the pitcher. It was pretty cool.
I am going to try this when I have some private time and I'll let you all know how it goes!