Question2Answer - A Q&A site helps an online community to share knowledge.
Stack Overflow - Community-based Q&A part of the Stack Exchange platform.
The Answer Bank - The Answer Bank is the UK’s leading question-and-answer site.
Stack Exchange - Stack Exchange is a fast-growing network of 84 [and counting] question and answer sites on diverse...
wikiHow - wikiHow is a wiki based collaboration to build the world’s largest, highest quality how to manual.
AskBot - Askbot enables users to create Q&A forums.