Free ebook: Moving to Microsoft Visual Studio 2010 (10 chapters by by Patrice Pelland, Pascal Paré, and Ken Haines)
Free ebook: Programming Windows Phone 7, by Charles Petzold (a 24-chapter gift from the Windows Phone 7 team and Microsoft Press)
Free ebook: Introducing Microsoft SQL Server 2008 R2 (10 chapters by Ross Mistry and Stacia Misner)
Free ebook: Understanding Microsoft Virtualization Solutions (Second Edition) (6 chapters by Mitch Tulloch)
Free ebook: Own Your Future: Update Your Skills with Resources and Career Ideas from Microsoft (8 chapters by Katherine Murray)
Free ebook: Introducing Windows Server 2008 R2 (9 chapters by Charlie Russel and Craig Zacker)
Free ebook: First Look Microsoft Office 2010 (14 chapters by Katherine Murray)
Free ebook: Deploying Windows 7, Essential Guidance (10 chapters from the Windows 7 Resource Kit and 6 TechNet articles)
All download link here on MSDN Blog