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
Clearbit - Clearbit provides Business Intelligence APIs
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.
ZoomInfo - ZoomInfo is a B2B database providing detailed business information on people and companies.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
InsideView - InsideView aggregates and curates all the company and contact data, news and social insights, and professional connections you need to do business better.