Talkus - Chat with your website users from Slack
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Aircall's Zendesk App - The best phone companion for Zendesk
Drift - A messaging app that helps you grow your business.
Drift for Slack - Talk to your website visitors & customers in real-time
HeyHi.sg - Video call with interactive whiteboard