Social networking alone is not hot news anymore. But adding to it the “interest graph” concept about finding out more of what you know and how it is related. 

Recently we started using Pearltrees, which was established in late 2009 as a tool for bookmarking and organizing web content.

They provide users with the options of creating trees of knowledge around a content they’ve found online in various areas of interest.

Check it out, it is very interesting tool!