I cam across this the other day and as we never find out the gender before the big day, thought I'd give it a go. The theory is, you get a teaspoon of bicarb in a cup, pee on it, it if fizzes you are having a boy, no fizz it's a girl.
Mine didn't fizz

Which would be funny if it is a girl, as DH and I are certain that we'll be having another girl.
Anyone who is pregnant and knows the gender willing to give it a try? I know it's just a bit of fun

Seems a bit safer than peeing on Drano though!
DD1 - December 2009 - breastfed for 22 months DD2 - January 2012 - straight back onto the booby feeding bandwagon