Etherpad

Etherpad (previously known as EtherPad) is an open-source, web-based collaborative real-time editor, allowing authors to simultaneously edit a text document, and see all of the participants' edits in real-time, with the ability to display each author's text in their own color. There is also a chat box in the sidebar to allow meta communication.

First launched in November 2008, the software was acquired by Google in December 2009, and released as open source later that month. Further development is coordinated by the Etherpad Foundation.