Question/Answer sites such as Quora are great places to learn new things about the topics that interest you. Of course, you are limited on what you can do on those sites. If you want to create your very own Q/A site using WordPress, the Q&A plugin can help. It turns your WordPress site into a fully featured Q/A site just like Yahoo! Answers. It is compatible with BuddyPress too.
The Q&A Plugin lets managing and editing questions easy. The features are added to your front-end but your visitors won’t have to see your admin panel to get started. Users can add and edit their questions and answers using the WYSIWYG interface available. Users can vote on questions. The reputation system is basic but useful.
The Q&A Plugin offers dedicated user profile pages. It can be integrated into your theme easily. The pro version provides you with even more features. The pro version lets you assign categories in addition to tags and questions. It also enables anonymous visitors to post/answer questions. Pretty neat plugin to use to start your own Q/A community.