Stack Exchange

Stack Exchange is a fast-growing network of 84 [and counting] question and answer sites on diverse topics from software programming to cooking to photography and gaming.

Free Android iPhone Android Tablet iPad Web

AskBot

Askbot is a Q&A system, like StackOverflow, Yahoo Answers and some others. Askbot is based on code of CNPROG, originally created by Mike Chen and Sailing Cai and some code written for OSQA.

Freemium Web Self-Hosted Django Python

Askalot

Askalot is a next generation CQA (Community Question and Answer) system.

Free Open Source Self-Hosted

LampCMS

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...

Free Open Source Self-Hosted PHP MySQL Community Edition MongoDB