Contents at a Glance 
The full Microsoft Application Architecture Guide is available for free on MSDN in HTML.  This is the contents of the guide at a glance:

• Foreword by S. Somasegar
• Foreword by Scott Guthrie
• Preface by David Hill

Chapters

• Chapter 1: What is Software Architecture?
• Chapter 2: Key Principles of Software Architecture
• Chapter 3: Architectural Patterns and Styles
• Chapter 4: A Technique for Architecture and Design
• Chapter 5: Layered Application Guidelines
• Chapter 6: Presentation Layer Guidelines
• Chapter 7: Business Layer Guidelines
• Chapter 8: Data Layer Guidelines
• Chapter 9: Service Layer Guidelines
• Chapter 10: Component Guidelines
• Chapter 11: Designing Presentation Components
• Chapter 12: Designing Business Components
• Chapter 13: Designing Business Entities
• Chapter 14: Designing Workflow Components
• Chapter 15: Designing Data Components
• Chapter 16: Quality Attributes
• Chapter 17: Crosscutting Concerns
• Chapter 18: Communication and Messaging
• Chapter 19: Physical Tiers and Deployment
• Chapter 20: Choosing an Application Type
• Chapter 21: Designing Web Applications
• Chapter 22: Designing Rich Client Applications
• Chapter 23: Designing Rich Internet Applications
• Chapter 24: Designing Mobile Applications
• Chapter 25: Designing Service Applications
• Chapter 26: Designing Hosted and Cloud Services
• Chapter 27: Designing Office Business Applications
• Chapter 28: Designing SharePoint LOB Applications

via - http://blogs.msdn.com/jmeier/archive/2009/11/05/now-available-patterns-practices-application-architecture-book.aspx