These are projects devoted to understanding the relationship between human diets and the diversity and types of microorganism species found living in the guts of the humans eating those diets. It is fascinating stuff. Did you know that scientists can predict, with 90% accuracy, whether a person is obese or not based on the microorganisms living in their guts?
Here is an awesome new article to read on the subject.
Anyway, you can donate to the American Gut Project and receive a test kit which can allow you to compare your gut microbiome to those of other people around the US and the world. Check it out.