‘Put article title here’ has to be Quora. Quora is basically a platform where people can ask questions and answers those posted by others. This feature was once part of Linkedin but for some weird reason Linkedin has decided to remove it.
The quality of questions and answers on Quora has pretty much blown me away. There are also a few famous people answering questions as well. For those who thrive on knowledge this IS the social network to spend time on (and get rid of facebook addiction).
For finance enthusiasts I have found a few good Q/A threads which I am listing below.