Oh my. I think I'm going to get my fillings removed after watching this.
 

And here's a study showing health improvements in people who have the metal removed from their mouths, in case you're not convinced.

Edit... Now I'm confused. This article contradicts the other evidence... Sigh... Why are things not more clear-cut?

Edit 2... I've changed my mind again. There is no way that mercury can be good for you at any dosage, although removing it can be very dangerous. What should I do?

Check this amazing video out. It shows what mercury does to the development of neurons in the brain:

And this VERY LONG pdf contains a huge number of research summaries pointing to the dangers of mercury:

http://www.iaomt.org/articles/files/files303/FDAcomment.pdf

Edit 3: Related to this, there is a lot of debate at the moment regarding childhood vacines (many of which use mercury-based preservatives) and a possible autism link. In 2002-2003, a bunch of studies were published, casting doubt on this link, but have a look at this document showing vaccine manufacturer involvement in these studies. I feel a bit like a conspiracy theorist here, but these are pretty serious accusations, none the less.