I have been using Quora since more than a year. I can say that its one of the best sites. its a question answer site. The topics ranges from varied stuffs. Science, Technology, Food, Gaming, Coding, Buildings, Space, Geology, Mathematics, Human Behaviour, Anatomy, Travel and everything else in the world. It is a great source of information.
Once you log in, You just cannot log off before at least half an hour. So much are the questions interesting. We have various options to do on Quora: Follow, Ask to answer(A2A), Upvote, Downvote, Mark answer in reading list, Edit answers and many more features added in recent update. Many renowned people in politics, Hollywood, food experts, NASA scientists, Entrepreneurs as well as Authors have their account on Quora. And the best part is that they even reply to your queries. If you are genuinely interested in learning and increasing your General Knowledge, Sign Up to Quora.
PS: Let me tell you its the best site for seeking knowledge on various topics. You cant update status on Quora:P