Social Bookmarking has always been a good backlink generation method. Here is a guide on how to use google+ as Internet Marketers to increase your search engine visibility, increase traffic and increase sales. Google+ has collected over 400 Million Members since its launch 2011 due to the massive number of people using it free gmail service and the ease to "add" google + to the current gmail account.
Pligg is an open source content management system that lets you easily create your own social network.