This is an excellent intro for those wanting to get up to speed. You need to spend some time with the HOLs if you haven’t done much SL before, but it will be worth your time.
From the description:
“The Silverlight 4 Training Course includes a whitepaper explaining all of the new Silverlight 4 features, several hands-on-labs that explain the features, and a 8 unit course for building business applications with Silverlight 4. The business applications course includes 8 modules with extensive hands on labs as well as 25 accompanying videos that walk you through key aspects of building a business application with Silverlight. Key aspects in this course are working with numerous sandboxed and elevated out of browser features, the new RichTextBox control, implicit styling, webcam, drag and drop, multi touch, validation, authentication, MEF, WCF RIA Services, right mouse click, and much more!”