For those who have not seen it yet Microsoft teams who work on Office 365 have created a hub on GitHub.
What are you going to find there?
Examples of code made by Microsoft and the community
Demonstrations presented during the sessions from Microsoft and the community
Part of the 'documents' sources for the MSDN documentation
SDK for 'third' platforms (IOS, android...)
The message behind that is Microsoft is investing in the community and wants to create a single place where developers (from any platform) can meet to participate in the projects together and share content. Therefore do not hesitate to have a look and to submit content / patches / projects.
Check out http://dev.office.com too!