yammer

With Yammer and Office 365 you can gain an Enterprise Social Network that transforms your business from the inside out, and brings collaboration to a new level.
Through Yammer and Office 365, you can tap into your network to find exactly what you need and discover things you didn’t know to quickly make decisions and get things done faster. Your employees can not only collaborate right within Office 365, but have a voice, getting the org chart out of the way to move your company forward. In fact, it’s such a powerful feature that Yammer comes standard with every Office 365 Enterprise E1 and E3 plan.