Yammer is a communication tool developed as part of the Office 365 suite of applications. This platform allows you to communicate with teachers and students as well as share information and host meetings. Conversations are broken into channels which could be classes, sections, groups for projects, topics, or whatever best fits your class. In each channel, you can post files, make announcements, respond to others, and more. You also get detailed analytics that can show the activity of everyone in your group so you can monitor how engaged your students are.