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

Chatlio - When you have a business to run, your average instant messaging software just will not do. You need an internal presence upon which your entire team can collaborate on. Read more about Chatlio.

Avochato - Text messaging for your business.

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.