OSQA - OSQA is the free, open source Q&A system you've been waiting for.
Wiki Answers - Answers.com: Wiki Q&A combined with free online dictionary, thesaurus, and encyclopedias.
Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
askalo - In May 2017, askalo was relaunched as a free classifieds search engine for cars, jobs and real...
Super User - Super User, part of https://alternativeto.
Fluther - Question and answer service based on user profiles and a user score.