Trillian - Trillian is a decentralized and federated instant messaging platform that lets your whole company send private and group messages, keep tabs on what co-workers are doing, share files, and much more.
Dingtone - Dingtone is a free call and texting application for making unlimited calls and text messages to any number at the moment registered in any part of the world by any cellular company.
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Textnow.com - It lets you text your friends, aka my only source of happiness
Skype - Stay in touch with your family and friends for free on Skype. Download Skype today to chat and call on desktop and mobile.
FluffyChat - Open. Nonprofit. Cute ?