Ask Me Anything - The official Reddit AMA app
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.
Code Duet - Finding a partner for pair-programming in 5 minutes
CodeShare.io - Realtime code sharing for developers
One Degree - The Human Search Engine
CodeTogether - Live share IDEs and coding sessions. See changes in real time.