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.
Unsee - The ability to open a chat session and message then delete it from history forever just like tlk.
Chatib - Chatib is an online chat room where you can meet and chat with new people, make them friends, or even data them online.
Chatango - Add free live chat to any web page. Chatango is a live group on your site
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.
Walkaround - Walkaround is a variant of Wave, based on the Apache Wave code base, that runs on App Engine.