Wow, I love Oobleck. I've never done it before but I read/heard about it from other friends and blogs. It's so neat. Well, okay, it's also really, really messy.
So, if you've never done it before, do it now - your kids will thank you.
(p.s. There are bunches of "recipes" out there on the web. I did something like 3/4 c. cornstarch and maybe 1/3 -1/2 c. water? or more? I don't know. If you don't know what's so special about it, I'll tell you: you squeeze it real tight in your hand and you can make a ball, open up your hand and Oobleck just "melts" or liquidfies. It's awesome.)