Human Microbiome Project

There's a story in the Economist about the beginning of this project that aims to examine the diversity of bacteria that live in "the intestines (which are home to most of them), the skin, the nose, the mouth, the throat, the respiratory tract, the stomach and the vagina."

"Besides the 10 trillion human cells in a body, there are another 100 trillion bacterial cells"

There are obvious applications to health, as well as to human population genetics.