Ace of Spades links to an article at the Telegraph about a gel type substance that hardens when hit at high velocity. The gel, called D3O, will be tested to see if it will stop bullets when integrated into Soldier's helmets.
I'm kicking myself in the ass right now because I thought of this years ago when I was a kid. My parents had bought me one of those Stretch Armstrong figures that are made of something that's probably similar. If you've ever owned one of those things then you know what I'm talking about; you can manipulate the figure and stretch him all day, and he will feel flexible. Punching him, however, would break your hand because the gel stuff inside hardened up.
Even as a kid I though it would make for some pretty cool armor. Too bad I didn't act on it or I could be reaping the big bucks instead of working my ass off.