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.

Chatib - Chatib is an online chat room where you can meet and chat with new people, make them friends, or even data them online.

Otr.to - A secure peer-to-peer chat in your web browser.

Kandan - Open Source private chat server. Your own private Chat server in minutes, plus additional features.

ChatSecure - ChatSecure is a free and open source messaging app that features OTR encryption over XMPP.

Chattusa - Chattusa is a social network website that provides a free chat service and lets you connect with people from the USA without any hassle.