ChatSecure - ChatSecure is a free and open source messaging app that features OTR encryption over XMPP.
ChatIW - Meet and Chat with new friends around the world.
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.
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.
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.