I know a guy who will give one million dollars to anyone who can prove dowsing rods work.
Seriously.
I've started on this book...
[ame=http://www.amazon.com/Water-Witching-U-S-A-Evon-Vogt/dp/0226862984/ref=sr_1_1?ie=UTF8&qid=1378772597&sr=8-1&keywords=water+witching+usa]Water Witching U.S.A.: Evon Z. Vogt, Ray Hyman: 9780226862989: Amazon.com: Books[/ame]
It gives a fascinating history behind the "craft", which is hundreds and possibly thousands of years old.
My grandfather made a decent living with the pendulum and when my uncle inherited it, he and my dad did the same.