Personally, I've found that running clubs attract diverse groups and tend toward activities that create ample opportunities for smalltalk and meeting people with shared interests outside of the sport. This doesn't hold true for most other sporting activities, in my experience.
Interesting. I was a decent runner in high school, way back. I'm a cyclist now, but I found that cycling groups tend to either be focused on athletic performance or activism and I don't particularly care for either at this point. I'll have to try some running groups as there are a lot of local ones.