Here's Part 4 of Charles Murray's intervew with Peter Robinson on social capital. When I first heard Murray discuss social capital, I did a Venn diagram of the positive communities (even including the virtual community of Maggie's Farm) of which I am a part. It was illuminating, and I think I can say that I am quite involved in my community and in many sub-communities and thus have a good store of social capital in Murray's use of the concept.
Of course, my religious communities are there, too. Mead discusses here: Religious Are Key to American Revival. I don't particularly enjoy apologetics for religion which include things like "it's good for society," or "it's good for you," but he makes some points.