I'm a homebrew (beer) nerd. The global community is very warm and welcoming for people at all levels. Everyone is interested in building each other up, and it promotes experimentation and precision. As far as niche communities go, there's a very strong but surprisingly small underground of sour beer enthusiasts. http://www.milkthefunk.com/ is an online forum and massive wiki dedicated to discovering and sharing new methods into souring beer. Some of the most well known sour beer brewers contribute and use it as a resource.