Windows/Linux only: If you're looking to collaborate in real-time on a writing or programming project, then check out MoonEdit. It's a tiny download that, when installed, will allow you to host sessions with other MoonEdit users. Each user is giving a nickname and a colour, and cursors and highlights appear for all. The finished files can be output in the native ME format to preserve meta-data like who edited what, standard TXT format or an HTML file that will display the text for non-MoonEdit users which includes the colours and other notes. You can change options through drop-down menus or through a command line editor. It's not as tricked out for coders with syntax highlighting and line numbers like similar tool Gobby, but it will evaluate mathematical statements you've typed out after hitting Control+Enter, including produce random numbers (if, say, you wanted to play some Dungeons and Dragons with friends). And there is also a neat tool for sequencing music directly within the interface! MoonEdit is a free download for Windows and Linux.Thanks pennstatephil!