Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Drift - A messaging app that helps you grow your business.
Intercom Facebook integration - Read, manage & respond to Facebook messages from Intercom
Drift for Startups - Grow your early-stage startup with this 95% off discount
Crypton.sh - SMS - Secure Anonymous SMS in the cloud (and a phone number)
SendBird - SendBird is messaging-as-a-service.