While normally not my cup of tea (and I tend to disagree with their explanations for the phenomenon) I came across this blog that talks about the various mysterious valleys around the world.

If you are a believer in UFO's, then this site might be something you will want to add to your favorites.

Edit:

Another UFO blog is posting this story, apparently aliens are now enjoying causing the sky to go black in the UK.

So here is yet another blogger that enjoys tracking the phenomenon.