Paraskevidekatriaphobia? Jaw-Breaker of a Word for Fear of Friday the 13th

"Why Friday the 13th Is Unlucky"
About.com

The first paragraph tells you that this isn't going to be one of those fluffy articles:

"I have before me the abstract of a 1993 study published in the British Medical Journal provocatively titled, 'Is Friday the 13th Bad for Your Health?' With the aim of mapping 'the relation between health, behaviour, and superstition surrounding Friday 13th in the United Kingdom,' its authors compared the ratio of traffic volume to the number of automobile accidents on two different days, Friday the 6th and Friday the 13th, over a period of years."

It's pretty good reading, though, if you want an in-depth look at the psychology, history, and weirdness of Friday the 13. You'll even learn that there are two ways to spell "paraskevidekatriaphobia," and who coined the word.