Unsee - The ability to open a chat session and message then delete it from history forever just like tlk.
Anologue - Disposable online chat.
Chatango - Add free live chat to any web page. Chatango is a live group on your site
Shtuff Chat - Free Group / Team chat with persistent history.
Walkaround - Walkaround is a variant of Wave, based on the Apache Wave code base, that runs on App Engine.
Meet in Chat - Meet new people. Have fun sharing photos.