Etherpad Lite up 'n' running in 5 minutes

Forever aloneEtherpad Lite is a lightweight version of (probably) the most popular web-based collaborative real-time editor - Etherpad. This great peace of software allows multiple users to edit the same document in real-time. To make collaboration easier, users have built-in chat at their disposal. History playback, infinite undo, easy import and export of documents are some of the cool stuff it has to offer.

Compared to the original, EL has very short system requirements list, which makes it very easy to deploy. Since it's written in server-side JavaScript using Node.js, to make it functional for testing/development purposes you'll need only Node.js, but for everyday/production usage it's recommended that you use a web server (e.g. Apache or Nginx) and MySQL.