WPF/e and Expression on Channel9
If you're interested in learning more about Expression, WPF, and WPF/e, here is some content straight from the horse's mouth. These Channel9 interviews are with the Expression team, and have some great information about the software, how its been developed, and the direction of Expression and WPF/e in the future.
In particular, if you don't know anything about WPF/e, you will definitely enjoy the last video.
Check them out!