GetSatisfaction - Get Satisfaction is the leading customer engagement platform that helps companies build better relationships with their customers and prospects, through the best online customer community.
Feedbackify - Feedbackify offers website feedback solutions that enable companies to engage with their customers.
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
tawk.to - tawk.to is a free live chat app that lets you monitor and chat with visitors on your website or from a free customizable page
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.
Userlike - Userlike is free live chat software for website and mobile support.