Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
LiveChat - LiveChat - premium live chat software. Approach customers directly on the website, make connections and drive more sales using LiveChat.
HelpSpace - The team inbox with super powers
Olark - Real-time chat and monitoring of your website visitors through Google Talk and Jabber.
Drift - A messaging app that helps you grow your business.
Zendesk - Zendesk is a beautiful, lightweight help-desk solution.