UseResponse - Open-source, self-hosted customer feedback software, live chat and helpdesk system that you can install on your server. Organize documentation using knowledge base and get feedback from social networks with centralized system

Blurtit - Blurtit is a Q&A website. You can ask a question or answer on any question.

UserVoice - UserVoice integrates easy-to-use feedback, helpdesk, and knowledge base management tools in one platform that empowers users to speak and companies to understand.

wikiHow - wikiHow is a wiki based collaboration to build the world’s largest, highest quality how to manual.

idea.informer - Idea Informer is a idea forum similar to uservoice or getsatisfaction.

AllAnswered - Your Team's Collective Brain All-In-One Knowledge Management System Wiki + Q&A + Workflow + AI