The Expression Blend material is presented by Lee Brimelow (author of the well known blog thewpfblog.com) and progresses through from a basic overview of the tool to specific techniques for dealing with text, animation, 3D, media, layout, controls and data. There's just over sixty individual nuggets - Dr Sneath prescribes that you take two a day for a month and you'll feel great!
I haven't looked so closely at the Expression Design material, but it's similarly comprehensive if the syllabus is to be believed. Ted LoCascio is the author of the six and a half hours of material available here.
They also have paid-for material on many other topics, including Expression Web. My only frustration is that they missed a trick by producing the material in QuickTime format. Hopefully they'll see the light, install Expression Media Encoder and transcode these to Silverlight, at which point they can make them available via Silverlight Streaming and save a bundle in bandwidth costs!
More free training coming soon... keep an eye on the blog for details.