Here is a random selection of links on Expression, mainly WPF/E that I collected after the 4 December announcements.  

James Clarke's Weblog  Great series on 4 December announcements

TheWPFBlog   Designer at Frog Design

Mike Harsh's Blog Mike is a program manager for WPF and has a great blog on the technologies.

Embedding video in your blog using WPF/E  Chandra Thota is another program manager here at MS.

Twelve videos in WPF/E  Mike Taulty another Microsoftie showing an experiment running 12 videos at once in WPF/E

 

A number of other links can be found on Wikipedia here.

 

For developers, there are a number of links that you could check out:

 

Unfortunately there isn't much out there by designers for designers. Let me know if you see anything.