Houseparty - Brining empathy to online communication.
Live Chat by Sumo.com - Instantly communicate with customers, prospects & visitors
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
Intercom - Intercom is a customer relationship management and messaging tool for web businesses. Build relationships with users to create loyal customers.
Rume - Video chat that doesn't feel like work
GoSquared Live Chat - Beautiful, simple, and free live chat for your website