Jitsi - Open-source video calling and chat platform.
MagicPad - Free, simple, and private, offline text encryption suite.
Gajim - Full featured and easy to use Jabber client
i2pd (I2P Daemon) - i2pd (I2P Daemon) is a full-featured C++ implementation of I2P client
Psi - Psi is a multi-platform and standards-based instant messaging client available for Windows, Linux, Mac and more.
Jami - Application and Data, Collaboration, and Web and Video Conferencing