Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Feedbackify - Feedbackify offers website feedback solutions that enable companies to engage with their customers.
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
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Userlike - Userlike is free live chat software for website and mobile support.
User.com - A marketing automation platform to enhance personalized communication and streamline business processes. Improve sales, customer success, and marketing processes with a single automation tool.