Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Zopim - Live chat is a faster and more personal way for you to engage your customers. Free for 14 days. No credit card required.
Smallchat Beta - Slack integration for chatting with visitors to your website
Crisp Chat - Multi-channel customer support software
HelpSpace - The team inbox with super powers
Mutiny - Personalize your website for each visitor