Microsoft 365 is an online version of Microsoft's well known Office suite. Office 365 for Education is free for schools and is already being used by many public school districts and colleges.
Office 365 is cloud based and includes Microsoft Office Web Apps, Exchange Online, SharePoint Online, and Lync Online.
This is Microsoft's answer to Google Apps for Education. It can be a good option for schools that are heavily invested in Microsoft apps as there would be almost no learning curve or training required. It includes Word, PowerPoint, Excel, Email, Calendars, web sites, and much more, including the ability to collaborate online with others and even run an online course.
You can find more information about features here. (including deployment guides and training)
You can go here to register: http://www.microsoft.com/education/en-us/products/Pages/office-365-for-education.aspx
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