Here is a couple of examples by Petzold:
Let There Be Shadows[
^]
Let There Be Shadows (Part II)[
^]
You may find the
WPF3D Team Blog[
^] to be of some interest.
The
XAML Exporter for Blender[
^] allows you to export to xaml from
blender[
^] - there are limitations on it's abilities to deal with lights and shadow, among other things, but if what you want is reasonably simple, it will do.
While it's possible to do a lot of 3d stuff in xaml -
XNA[
^] offers a more efficient programming model.
Best regards
Espen Harlinn