WordPress.org

I am biased. I am the co-founder in Pubble. We built Pubble to make it really easy for anyone to add great Q&A to their website, Facebook page or blog. For WordPress users, we built a custom plugin that is optimised for use on WordPress sites. The big idea with Pubble is to get everywhere you live online working together to build a great Q&A community on your site. You see, we believe that for Q&A to be really effective, it should live in context (i.e. on top of the pages that the questions relate to). With this approach, every page on your site will get a little richer every day. As the Q&A dataset grows, Pubble will start delivering instant answers for frequently asked questions. You can add Pubble to your WordPress blog now for free. If you want to give it a go, you can Get Started here. Thanks, John

have been using it on a couple of blogs and sites that I run, and it works really well. Uses FB, Twitter and Linkein Auth, allows for reposting via email. Nice, neat, works, easy to install.