WordPress.org

You create the questions or let your users ask the questions or both. You decide.... Search, Read and Answer questions from your users and get notified by email when a new question is asked. When you answer a question the user gets email notification of the answer. View everything on one page or post using our tabbed interface or add different sections to each page or post using easy shortcodes. Now uses the rich text editor to answer questions for those with permission to use it. By [twentyfiveautumn.com] (http://twentyfiveautumn.com) and released under the [MIT license] (http://opensource.org/licenses/MIT).

Requires WordPress 3.2 and PHP 5