Microsoft's Mike Harsh just released an updated version of his WPF/E Pad that makes it easy to quickly test out XAML using the WPF/E viewer. Pretty cool stuff! Since I'm a big fan of XML I'm really excited about what WPF/E offers.
My good buddy Simon Allardice (who also works at Interface Technical Training) has posted several cool demos on using WPF/E at the following links as well: