I don’t know if it’s the best or the biggest, but DC has one damn well organized community of data enthusiasts:
Data Community DC (DC2) is an organization formed in mid-2012 to connect and promoting the work of data professionals in the National Capital Region. We foster education, opportunity, and professional development through high-quality, community-driven events, content, resources, products and services. Our goal is to create a truly open and welcoming community of people who produce, consume, analyze, and work with data — data scientists, analysts, economists, programmers, researchers, and statisticians, regardless of industry, sector, or technology. As of January 2014, we are currently over 5,000 members strong from diverse industries and from a large variety of backgrounds.
But that’s what we do here in the DMV, build bureaucratic organizational structures. Ha, ha! Only serious.