Working with XAML code in VS2008 I have just found that I can easy jump to class's or property definition. If I press CTRL and click left mouse button on certain class or property in XAML I will be immediately switched to Object Browser (if it is class or property of .NET or external dll) or to class's or property definition in my code (if it is class or property from my sources).
Eugene Dolinskyy just pay my attention that "clear" VS2008 doesn't have this possibility. This feature is presented by ReSharper.