Windows Vista Development Center: http://msdn.microsoft.com/windowsvista/
This is the starting point for information on Windows Vista development.  

Understanding Windows Vista Development: http://msdn.microsoft.com/windowsvista/understanding/default.aspx

Links to guides outlining the various key features/pillars around Windows Vista development: Security, Reliability, Integration, Discover info/data, etc.

WinFX Developer Center: http://msdn.microsoft.com/winfx/

WinFX, the set of next-generation managed APIs provided by Microsoft, information and development tools are going to be positioned here.  There is currently info on developing applications with WinFX, links to documentation, code samples and the SDK are all available from this site.

Windows Presentation Foundation: http://msdn.microsoft.com/windowsvista/building/presentation/

WPF provides the foundation for building applications and high fidelity experiences in Longhorn, blending together application UI, documents, and media content. The functionality extends to the support for Tablet and other forms of input, a more modern imaging and printing pipeline, accessibility and UI automation infrastructure, data driven UI and visualization, as well as the integration points for weaving the application experience into the Windows shell.

 Windows Presentation Foundation Hands-On-Labs: http://msdn.microsoft.com/windowsvista/building/presentation/hands_on_lab/default.aspx

The Hands-On-Labs are a set of tutorials that introduce key features of Windows Presentation Foundation. Each lab guides you step-by-step through the process of developing a complete Windows Presentation Foundation (WPF) application using Visual Studio 2005, the WinFX SDK and the Visual Studio 2005 Extensions for WinFX.

 Windows Communication Foundation (formerly code-named "Indigo"): http://msdn.microsoft.com/webservices/indigo/default.aspx

A set of .NET technologies for building and running connected systems. It is a new breed of communications infrastructure built around the Web services architecture. Advanced Web services support in Windows Communication Foundation provides secure, reliable, and transacted messaging along with interoperability.