Just came across this new WPF\Silverlight site – nibbles: snack tutorials for hungry designers.
As described on the site:
As the name suggests, nibbles are short tutorials that teach you one specific feature at a time. Later, you can combine all the things you have learned to develop a complex project by yourself.
There are already some tutorials about Expression Blend and Silverlight and content on Blend with WPF is expected soon. You can watch for new releases on the nibbles blog.