Most of us have heard at some point or another that we have entire ecosystems of microbes living in our gut. Mostly of these microbes are happy symbionts that help us digest our food, but some can occasionally becoming pathogenic and cause health problems. Have you ever wondered what your gut microbial community looks like? Now you can find out! The Earth Microbiome Project (http://www.earthmicrobiome.org/), founded several years ago with the ambitious goal of “sequencing the microbiome of planet earth”, (or, in other words, characterizing basically all of the genetic diversity that exists on our planet), has begun a smaller, more targeted project with the aim of characterizing the gut communities of human populations.
Some of the key science questions driving this project : to what extent do gut microbial communities vary among people? At what scales can we discern patterns in microbial community composition? Are similar microbial communities found among people from similar geographic regions, with shared genetic history, or with a shared diet? And, perhaps more interestingly to most of us, to what extent does the composition of our gut community impact our own health? Once we have enough data to start answering some of these basic questions, perhaps we can even start making predictions about what sorts of lifestyles will lead to what sorts of gut flora, and how these communities, in turn, will impact our overall health.
It costs just $100 to join and get your microbiome sequenced. And the information could change your life!
wyrdscience 
It would be interesting to try to correlate these microbial gut communities with regions noted for their extreme longevity. I imagine this study will try to do that.