Question2Answer - A Q&A site helps an online community to share knowledge.
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Fluther - Question and answer service based on user profiles and a user score.
Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
wikiHow - wikiHow is a wiki based collaboration to build the world’s largest, highest quality how to manual.
Discourse - Discourse is an open source discussion platform built for the next decade of the Internet.