They include : Windows 8.1, Windows 8, Windows 7, Office 2013, Office 365, Office 2010, SharePoint 2013, Dynamics CRM, PowerShell, Exchange Server, Lync 2013, System Center, Azure, Cloud, SQL Server, and much more.
They can be found at this link:
http://blogs.msdn.com/b/mssmallbiz/archive/2014/07/07/largest-collection-of-free-microsoft-ebooks-ever-including-windows-8-1-windows-8-windows-7-office-2013-office-365-office-2010-sharepoint-2013-dynamics-crm-powershell-exchange-server-lync-2013-system-center-azure-cloud-sql.aspx