LampCMS is an full-featured Open Source Question and Answers web program written in PHP with deep integration with Facebook, Twitter, Google, Linked-IN, Tumblr and Blogger APIs
It uses MongoDB as a database to achieve speed and scalability.
Question/Answer websites are becoming very popular, many people find them to be a better choice for building online communities than a traditional web forum.
Just like many other Question and Answer sites, LampCMS is tag-based, but it also has support for categories and unlimited sub-categories.
Some people have been referring to LampCMS as an Open Source StackOverflow and Quora crossover. All we can say is there are certainly several features similar to those of StackOverflow and several similar to Quora but this program also has some features similar traditionally found in popular Forum Software like "Sticky threads" and "Dot folders"