I should use StackExchange more...

Stack Exchange is a network of individual Q&A free websites (99 of them!) covering very narrow field specific topics. Anyone can contribute by offering their expertise and answering or rating answers to thousands of questions.

Examples of Stack Exchange websites include:

http://math.stackexchange.com/ - for Math lovers
http://skeptics.stackexchange.com/ - for random question
http://photo.stackexchange.com/ - for photography gurus
http://cstheory.stackexchange.com/ - for programmers

Since the 99 available websites cover many different fields of knowledge the demographics of the users varies widely. Most of the users are male in their 20s and 30s. This could be related to the fact that a lot of the topics discussed are very technical. The traffic mostly comes from USA and India - leading countries in software development.

Stack Exchange will be very useful to anyone interested in computer science, math, video games, physics, etc. People of all levels of expertise can contribute. Rookies can ask questions and vote for the answers. Users with proved knowledge of the subject can actually suggest answers and solutions to the problems posted.

I personally use Stack Exchange to find answers to programming questions. However, after doing the research I've discovered that the website could be useful for other topics like traveling and cooking as well. Overall, I highly recommend this social network as a source of valuable and verifiable information.