Element.io - Secure messaging app with strong end-to-end encryption, advanced group chat privacy settings, secure video calls for teams, encrypted communication using Matrix open network. Riot.im is now Element.
Keybase Chat - End-to-end encrypted chat built into Keybase
Chatib - Chatib is an online chat room where you can meet and chat with new people, make them friends, or even data them online.
Pithos - pithos is a daemon which provides an S3-compatible frontend for storing files in a Cassandra cluster.
Kandan - Open Source private chat server. Your own private Chat server in minutes, plus additional features.
Pandora - Pandora Radio is a free (ad-supported) internet radio founded in 2000.