Quora is described as 'People come to Quora to ask questions about any subject, read high quality knowledge that's personalized and relevant to them, and share their own knowledge with others. Quora is a place to share knowledge and better understand the world' and is a very popular Q&A service in the education & reference category. There are more than 50 alternatives to Quora for a variety of platforms, including Web-based, Android, iPhone, Android Tablet and iPad apps. The best Quora alternative is Reddit, which is free. Other great apps like Quora are Stack Overflow, Stack Exchange, Slant and Super User.
I've been using CodeProject for years (since it first went started), and continue to rely on it for programming and development knowledge often.