From ThinkGeek:

'' 'kung fu' means skill from effort. 'kung foo' means skill from badass-programming-powers. Wear this shirt and you will receive the honorary title of white belt in kung foo (hey, we're easy). Black belts are a bit more complicated. You'd have to be able to visualize multiple systems of data hierarchically in your head while writing obfuscated device drivers for i386 boxes. Blindfolded. No caffeine. And that's just for a first degree black belt in Kung Foo. ''

For some pictures of the shirt, go to http://www.thinkgeek.com/tshirts/coder/28f4/

-- BenLewis