Whether you're an experienced user, or you are new to Expression Design, the Expression team blog is a great resource for learning and reference material. Below is a list of articles and tutorials currently available on the team blog site.
Creating your Own Vista "Chrome" Style Button
Using Brush Strokes to Create a Design
Two of the Best Kept Secrets in Expression Design
Trick or Treat : Resolution = 96 PPI
Creating a Vista Style Button Template
Glassy Feed Buttons in Expression Design
Removing backgrounds from photos
Blending Photos
Check back often as new tutorials are added frequently. Better still, add the team blog to the RSS Feeds section of Microsoft Outlook, or to your favorite RSS Feeds program, to be alerted when new content is added.
Another great source of learning material is the Microsoft Expression Design Support Team Blog, maintained by our Design Support Engineer, Will Buffington.
If you know of other sources of Design tutorials, feel free to post them here.
Annie