I came across this post on MSDN by Ray Fleming from the Microsoft UK Education Team and in it he highlights several free Microsoft e-books that you can grab.

Here is the summary of the books he mentions:

• Free ebook: Programming Windows Phone 7, by Charles Petzold
  24 chapters from the Windows Phone 7 team and Microsoft Press
• Free ebook: Moving to Microsoft Visual Studio 2010
  10 chapters by by Patrice Pelland, Pascal Paré, and Ken Haines
• Free ebook: Introducing Microsoft SQL Server 2008 R2
  10 chapters by Ross Mistry and Stacia Misner
• Free ebook: Own Your Future: Update Your Skills with Resources and Career Ideas from Microsoft
  8 chapters by Katherine Murray
• Free ebook: Understanding Microsoft Virtualization Solutions (Second Edition)
  6 chapters , 450+ pages, by Mitch Tulloch
• Free ebook: First Look Microsoft Office 2010
  14 chapters by Katherine Murray
• Free ebook: Windows 7 troubleshooting tips
  Short ebook by Mitch Tulloch
• Free ebook: Introducing Windows Server 2008 R2
  9 chapters by Charlie Russel and Craig Zacker
• Free ebook: Deploying Windows 7, Essential Guidance
  10 chapters from the Windows 7 Resource Kit and 6 TechNet articles

As Ray mentions in his post, some of these are very technical but some are also great for non-technical geeks as well.

Enjoy.