Quora - Quora is a place to gain and share knowledge. It's a platform to ask questions and connect with people who contribute unique insights and quality answers.

Reddit - Reddit gives you the best of the internet in one place. Get a constantly updating feed of breaking news, fun stories, pics, memes, and videos just for you.

Wiki Answers - Answers.com: Wiki Q&A combined with free online dictionary, thesaurus, and encyclopedias.

Slant.co - Slant is a collaboratively edited resource that helps you quickly make decisions.

Raddle - A web-based forum where users submit links, pictures, posts, etc.

Question2Answer - A Q&A site helps an online community to share knowledge.