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
AskNicely - Collect customer experience feedback on a daily basis and empower your team to take immediate action to drive retention, upgrades, reviews and referrals.
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.
Delighted - The fastest and easiest way to gather actionable feedback from your customers
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Survicate - Collect feedback on your website and find out more about your visitors.