I'm sure everyone's seen this by now, pretty funny video of what happens when you mix diet coke and mentos and you don't have a girlfriend but you have a big back yard and a video camera.  Funny that is unti you realise that there's people starving in the world and these two dorks are spraying hundreds of litres of coke and lollies on their lawn.  Whatever rocks your boat I guess.  Here's their site, it's the best coke/mentos experiment I've seen yet:  Eepybird.com