Question2Answer is a free PHP/MySQL solution for social Q&A sites (like Stack Overflow or Stack Exchange). A Q&A site helps your online community to share knowledge. People with questions get the answers they need. The community is enriched by commenting, voting, notifications, points and rankings.
Features:
Takes 5 Minutes To Install Easy Styling With CSS Translations Custom Sidebar/Widgets Custom pages/Links SEO Features Captcha Support Integrated Search Engine RSS Email Notifications