And if you want to worry about esoteric possibilities...

[mmcirvin]

By the way, that NASA page holds many delights if you look at the really slim probabilities. Hey, how about this two-kilometer-wide asteroid? Chance of impact: about 1 in 2 billion. The sole possible impact date: May 19, 2006. That's so soon that if this turned out to be headed our way there's absolutely no chance we could do anything about it. Size and velocity: enough to do one hell of a lot of damage. The projected yield is 360,000 megatons TNT. This would devastate a huge region, and might even cause a global climatic catastrophe that would kill billions.

Of course, the chance that you'll get killed in a car accident tomorrow is way bigger.