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
NationBuilder - The world's first platform for leaders, handcrafted from scratch to help you grow your community and lead them to action.
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.
Crowded Communities - The all-in-one community platform.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Ning - Ning is the social platform for the worlds interests and passions online.