Vista Tutorial - WPF Application Framework

We are developing a WPF prototype where we are pulling together several of
our applications into a single application portal. I am concerned with
creating a single project that will house all of the Xaml files (for each
application) - mainly for maintainability and size of the project. Would
separating each of the applications into separate projects with a 'portal
project used to pull each of the separate applications for the UI. The
'portal or main project would run and show the key UI navigation tools
(ribbon, etc.) put would pull in the separate projects or dlls to the
display the specific Xaml for the selected application. Is there any info on
designing the framework for this setup using WPF for the UI.

Thanks