Another end of the world theory is that comet Elenin is not really a comet but rather a brown dwarf star, with planets revolving around it yet.  Our government supposedly knows that the close approach will destroy the earth.  Supposedly the last days of Earth will be September 26th or October 18th.  There are some YouTube videos posted by people who have done all sorts of convoluted calculations.  I find the truly scary thing is the certainty these people have that everything the government says is conspiratorial.  One woman even noted CBS' "eye" logo on TV and insisted it was a veiled message from the government to evacuate coastal areas and earthquake fault zones.  It's sad.  You can't reason with someone like that.