Hubski - Hubski is a community for sharing thoughtful information and conversation.
Mediamatters - Mediamatters or Media Matters for America (MMFA) is a nonprofit website with state mission of comprehensively monitoring, analyzing and correcting conversation misinformation in U.
Snapzu - Snapzu is basically reddit alternative.
Zimbio - Zimbio.
Stack Exchange - Stack Exchange is a fast-growing network of 84 [and counting] question and answer sites on diverse...
Tumblr - A feature rich and free blog hosting platform offering professional and fully customizable templates, bookmarklets, photos, mobile apps, and social network integration.