Recently I mentioned the release of a new guidance bundle by Microsoft Patterns & Practices, called the Modularity Bundle:
The bundle itself is essentially a repackaging of guidance provided awhile ago, but if you are interested in how you can build modular ( pluggable ) ASP.NET web applications using the Composite Web Application Block ( CWAB ), I have created a Modularity Bundle Screencast that walks one through the Modularity Bundle Quickstart and explains in detail how the CWAB works behind the scenes to provide pluggable and discoverable business modules and foundation modules for your ASP.NET Web Applications.
I hope you enjoy it! You can find the other 15 screencasts done to date on the Patterns & Practices Screencasts Page.
Download the screencast here.