The first Community Technology Preview of Acropolis is now available. So what is Acropolis? It is a set of components for developers to build modular, loosely-coupled .NET client applications, similar to the web parts framework in ASP.NET 2.0.
Acropolis builds on the strength of the Windows Presentation Foundation and CTP1 includes these features:
Declarative Composition - allows you to declaratively program the structure of application components
Navigation support - manages activation and deactivation of components
Document Life Time support - manages the life time of a document object
Layout Pane - Split style and tab style UI layout that leverages WPF
Transition Animation - Prepackage transitions built on WPF
More information and the CTP download is available at http://windowsclient.net/Acropolis.