List of social networking websites http://en.wikipedia.org/wiki/List_of_social_networking_websites

Online tools and applications http://www.go2web20.net/

Social Networking Tools http://www.jiscinfonet.ac.uk/infokits/social-software/networking 

5 Timesaving Social Networking Tools http://www.practicalecommerce.com/articles/2323-5-Timesaving-Social-Networking-Tools

Top 15 Most Popular Social Networking Sites | September 2011 http://www.ebizmba.com/articles/social-networking-websites

The Impact of Social Networking Tools and Guidelines to Use Them http://www.llrx.com/features/goodgoogle.htm