Code Duet - Finding a partner for pair-programming in 5 minutes
codebunk - Realtime Collaborative Editor with Code Execution, REPLs and Chat
Bing Intelligent Answers - Bing makes answers smarter using Reddit
Floobits - Floobits brings real-time collaborative editing to text editors, IDEs, and now Atom.
One Degree - The Human Search Engine
coderpad - Collaborative code editor with in-browser, real-time execution. Conduct programming phone screens like a boss.