Back in September 2005 at PDC, I gave a talk with Andres Sanabria titled PRS418: Developing Portal UI With Web Parts.

There are five separate demos:

1. ExternalWebParts: The WebParts and Connections for a page are stored in an external XML file, instead of the page itself.  Shows how to decouple the WebPart definitions from the page.  Illustrates the different phases of the WebParts life cycle.
2. ContentManagement: Customizes WebPart Personalization to implement a content management application.  Multiple versions of the personalization data are stored for each page and loaded dynamically.  Illustrates how to extend WebParts Personalization.
3. SecondaryIntefaces: Uses the "SecondaryInterfaces" feature of WebParts connections to implement a basic interface yet provide richer data on a second interface.
4. SecureImportExport: Uses a custom WebPartManager to encrypt the sensitive data in an exported .WebPart file.  The data can not be view or modified by the end user, and can only be decrypted by the web server that encrypted it.  Illustrates how to extend the import/export process.
5. WebPartsAdmin: Allows management of Personalization data via an external page.  Implemented by executing the target page in a child request.  Illustrates how to modify the personalization data on another page.