Open Whisper Systems
https://whispersystems.org/
Signal
Encrypted instant messaging and voice calling application for Android and iOS
Based on Open Whisper System
Client: open source
Server: Partially published under the AGPLv3 license and partially proprietary.
Signal protocol provides confidentiality, integrity, authentication, participant consistency, destination validation, forward secrecy, backward secrecy (aka future secrecy), causality preservation, message unlinkability, message repudiation, participation repudiation, and asynchronicity.
Telegram:
Cloud based instant messaging service
Also provides optional end-to-end-encrypted messaging
Open source client,
Closed source server
Telegram clients :
Mobile (Android, iOS, Windows Phone, Ubuntu Touch)
Desktop systems (Windows, OS X, Linux)
TextSecure