A social network is a social structure made of generally individuals or organizations that are tied by one or more specific types of interdependency, such as values, visions, ideas, financial exchange, friendship, sexual relationships, dislike, conflict or trade.
Sites that tracking Blogosphere,such as Technorati, BlogPulse, Tailrank, Spinn3r and BlogScope track the interconnections between bloggers. Taking advantage of hypertext links which act as markers for the subjects the bloggers are discussing, these sites can follow a piece of conversation as it moves from blog to blog. Sites also exist to track specific blogospheres, such as those related by a certain genre, culture, subject matter or geopolitical location.
Technorati: is an Internet search engine for searching blogs, competing with Google and Yahoo. Technorati was founded by Dave Sifry and its headquarters are in San Francisco, California, USA. Tantek Çelik was the site's Chief Technologist. Technorati uses and contributes to open source software. Technorati has an active software developer community, many of them from open-source culture. The site won the SXSW 2006 awards for Best Technical Achievement and also Best of Show. It was also nominated for a 2006 Webby award for Best Practices, but lost to Flickr and Google Maps.
Tailrank: is a site that provides a feed of content on the World Wide Web that's being discussed across the blogosphere. The site continuously scans blogs that have been registered with it, and composes an index of "top stories" that have been cited by the various blogs it has scanned.
Spinn3r: built by the same company as Tailrank, is a web service for indexing the blogosphere. It provides raw access to every blog post being published - in real time.
BlogScope: is a search engine for the blogosphere with advanced analysis and visualization technology. BlogScope is outcome of an ongoing research project at the University of Toronto. As of Oct 2007, the system is indexing around 120 million articles from 14 million weblogs.