social networks and discussion over content? Myspace, youtube are now well known - but who else are doing really interesting things to promote community and interaction between people? What are innovative sites in Europe or Asia? What other sites in the US?And is there one specific site that is helping people discuss content like a story, or news, or anything.

craigslist

The Usenet Newsgroups have been doing it for years, since long before there was a web. CompuServe used to do it until AOL bought them. I think they're gone now, but I left soon after the change. The Newsgroups still serve the purpose of promoting community and discussing areas of interest. (Some are much better than others at it.)