Zendesk - Zendesk is a beautiful, lightweight help-desk solution.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal 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
JivoChat - JivoChat is a live chat that enables you to talk to visitors on your website
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.
TextUs - TextUs is the leading businesses texting platform for professionals.