On TAPoR: http://tapor.ca/tools/922

Participad is a WordPress plugin that allows multiple people to edit the same WP content at the same time. Powered by Etherpad Lite, Participad gives you: notepads for collaborative notetaking; synchronous authoring of any content in the WordPress Dashboard; front-end editing. You can download it from the WordPress plugin repository.

Participad has three modules:

Dashboard – The Dashboard module puts Etherpad editors into the WordPress Dashboard. Participad removes the “Visual” and “HTML” tabs from the standard WP editor, and replaces them with a “Participad” tab.

Frontend – The Frontend module allows users to edit WordPress content from the front end of your website – no Dashboard required. Participad modifies the Edit links on your posts and pages so that, instead of leading to the Dashboard, the static content of your post is swapped with an editable Etherpad window.

Notepad – The Notepad module enables a new WordPress Post Type called Notepads. Notepads are collaborative note-taking documents, which can optionally be linked to existing static posts or pages. Participad provides several shortcodes and widgets that make it easy to create new Notepads from the front end of your website.

N.B. Participad requires a separate Etherpad Lite Installation.