Posterous, the blogging platform, has just launched a “Groups” feature that might be the easiest way to create a public or private social network on the web.

Instead of explaining it in detail here, I’m just going to recommend you visit a TechCrunch post that provides a better explanation than I could probably write.

I’m adding these links to Not “The Best,” But “A List” Of Social Network Sites and to The Best Online Tools For Collaboration — NOT In Real Time.