GitDuck - GitDuck is the easiest way to explain your code to other developers. Show how you code and record videos linked to your source code.
codebunk - Realtime Collaborative Editor with Code Execution, REPLs and Chat
CodeShare.io - Realtime code sharing for developers
Floobits - Floobits brings real-time collaborative editing to text editors, IDEs, and now Atom.
CodeTogether - Live share IDEs and coding sessions. See changes in real time.
coderpad - Collaborative code editor with in-browser, real-time execution. Conduct programming phone screens like a boss.