Gobby is a cross platform, open-source collaborative text editor that supporting multiple documents in one session in addition to a multi-user chat. It can run on Microsoft Windows, Mac OS X, Linux and other Unix-like platforms. The website offers screenshots so you can judge as to whether or not the editor might work for you before you download it. Some of the features include encrypted channel real-time collaboration, the ability to see cursors and selection done by remote users, session password protection, syntax highlighting for different programming languages. It looks very easy to use with a simple drag-and-drop functionality get documents into Gobby, go take a look.