Squad is a neat code creation and editing service that I learned about Kelly Tenkely who has students in her school writing code. Using the free version of Squad up to three people can collaborate on the creation of new code. They can chat in realtime to help each other work through challenging problems. A searchable chat record makes it easy to go back in time to see how a problem was worked out in the past.
Applications for Education
I really encourage you to read Kelly's post about Squad and Codecademy which she used to teach her students to code. In short, Squad makes it possible to jump in and help students when they need it.