SaaSiter Feed - Increase users engagement for your SaaS application.
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
Userlike - Userlike is free live chat software for website and mobile support.
Survicate - Collect feedback on your website and find out more about your visitors.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
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