Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Intercom Facebook integration - Read, manage & respond to Facebook messages from Intercom
Crisp Chat - Multi-channel customer support software
Crypton.sh - SMS - Secure Anonymous SMS in the cloud (and a phone number)
Drift for Enterprise - Automatically turn website traffic into sales meetings
Live Chat by Sumo.com - Instantly communicate with customers, prospects & visitors