When I think of an online community, I often think of the forums of the late 90s/early 2000s. Before social networks, these were the social gathering points on the web where discussions took place about politics, video gaming, music, and the little parts of life. This, in essence, is what a social community is. The members of these communities come together to discuss whatever they want to socialize. Think of this as a sort of cocktail party or in-person meetup.
Drowned in Sound is one of my favorite examples of a social community. Ever want to talk about your favorite bands with other passionate music lovers? A social community like Drowned in Sound fits the bill, but also expands into other topic areas its members are interested in.