Microsoft has released a new set of stencils for Visio that contain over 300 icons for creating infrastructure and workflow diagrams. Or, I guess you could just use them to create some funny cartoons to share around the office. Whatever your intent, this new set includes icons for Microsoft Office, Microsoft Office 365, Microsoft Exchange Server 2013, Microsoft Lync Server 2013, and Microsoft SharePoint Server 2013.
The stencils work with Visio 2003 or later, so you don't need the latest versions of Microsoft Office to use them. If you want to just view them (and, possibly make your own icons using screen capture software) you can download the Visio 2010 Viewer application.
I don't have Visio as part of my Office 365 subscription, but do still have Visio 2010 installed on my primary PC and they look great.
Download: New Office Visio Stencil