nocnoc - Instant group chat invite via link
Chalk - Chalk is a calculator that tries to do right what others do wrong.
Viber Communities - Group chat with up to 1B members, admin controls and more
chitchat - Chat Room with Selfies and Pagers (yes, pagers!)
Twist - Check fewer notifications, do more meaningful work. Twist is the team communication app for calmer, more organized, and more productive teamwork.
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.