This week I put oobleck (or ooblick) in a tub for the students to experiement with. If you haven't seen this stuff then you must try it at home. Simply mix corn starch and water, then prepare to be amazed. Oobleck is a non-newtonian fluid which means it acts like a liquid when being poured, but like a solid when a force is acting on it. You can grab it and then it will ooze out of your hands. Very neat indeed. I added orange liquid watercolor to ours to give it a pop of color.
If you want to see each step in the process (plus watch people walk on oobleck!) then click here.