Prism with Silverlight : Short Videos but covers topic really well

Creating a shell and modules

http://channel9.msdn.com/blogs/akmsft/creating-a-modular-application-using-prism-v2-part-1-of-4--creating-a-shell-and-modules

Visual Composition

http://channel9.msdn.com/blogs/akmsft/creating-a-modular-application-using-prism-v2-screencast-24--visual-composition

Implementing views and services

http://channel9.msdn.com/blogs/akmsft/creating-a-modular-application-using-prism-v2-screencast-34--implementing-views-and-services

Decoupled Communication

http://channel9.msdn.com/blogs/akmsft/creating-a-modular-application-using-prism-v2-screencast-44--decoupled-communication