There have been some great new additions this later time here : http://www.microsoft.com/sql/2008/learning/whitepapers.mspx
I would just point out these ones :
This 10-page paper discusses how the new spatial support in Microsoft SQL Server™ 2008 can help you to make better decisions through visual analysis of location data that can be stored and manipulated in a SQL Server database.
Focus: Spatial Data
SQL Server 2008 is secure by design, default, and deployment. Microsoft is committed to communicating information about threats, countermeasures, and security enhancements as necessary to keep your data as secure as possible. This paper covers some of the most important security features in SQL Server 2008. It tells you how, as an administrator, you can install SQL Server securely and keep it that way even as applications and users make use of the data stored within.
This 10-page paper includes: Introduction, Scale and Performance, High Availability, Security, and Manageability.
This paper discusses how Microsoft SQL Server 2008 builds on the management capabilities of previous versions and provides a variety of tools and frameworks to help you manage your enterprise data environment.
This 10-page paper includes: Introduction, Flexibility, Manageability, Scalability and Performance, and Conclusion.
Focus: Server Consolidation