How did they fail to mention Floobits?
Real-time collaborative editing with text editors and IDEs.
Supports Sublime Text, Atom, Neovim, Emacs and IntelliJ IDEA (which includes the family of editors, e.g. PhpStorm WebStorm PyCharm RubyMine, etc)
It can be pretty interesting to watch two people code in one of the public workspaces..