This is just hypothetical, but do you think a forum based around weather could work in this day and age? I know forums aren't the primary way people communicate online anymore, but thinking of niches I haven't seen any one really tackle is a community based around the weather. It's such a huge part of every day life and so many people often talk about the weather, heck on almost any forum you see there's a weather topic! Just recently Indonesia had a volcano erupt, there were some nasty storms that made their way through the Midwest in the US yesterday, and weather patterns are always changing. It would be a interesting community!