Psyced - This is psyced, a scalable multi-protocol multi-casting chat, messaging and social server solution...
MyChat - Secure instant messenger for any network
Jitsi - Open-source video calling and chat platform.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
i2pd (I2P Daemon) - i2pd (I2P Daemon) is a full-featured C++ implementation of I2P client
Encrypto - Encrypto lets you encrypt files before sending them to friends or coworkers.