Here's a link to a site called Bad Astronomy that attempts debunk a lot of the silly astronomy related myths and urban legends floating around out there. My favorite has always been the one about standing an egg on its end on the spring equinox. I was actually a victim of this for a long time since back around 4th or 5th grade my elementary school had a school gathering in the gym on the spring equinox so that our 4th grade science teacher could demonstrate this "fact" to everyone. I kept trying for several years afterward on the equinox to stand an egg up. Apparently I just sucked at standing eggs up since I was never able to really do it very well.
The author also attempts to debunk the tired old story about the moon landings being faked. This whole idea is just so ludicrous that I'm not sure any sane person can go about debunking it well. They seem to just get frustrated and start frothing at the mouth. People that believe this need to be sterilized and sent to live in the wilderness somewhere.