You thought Creationists were delusional?? Apparently, there are people that actually believe the Earth is flat, and that all the evidence to the contrary is part of a massive worldwide conspiracy.

http://news.bbc.co.uk/1/hi/magazine/7540427.stm
http://www.alaska.net/~clund/e_djublonskopf/Flatearthsociety.htm
http://en.wikipedia.org/wiki/Flat_Earth_Society

I wish I had some witty joke, but I'm simply left speechless.