Sharepoint Application Guidance available at
Overview from the website...
The Developing SharePoint Applications guidance helps architects and developers design and build applications that are testable, extensible, and that provide the tools they need to maintain those applications and diagnose problems when they arise.
This release contains a written guide, an API reference, two reference implementations, a set of reusable components and QuickStarts. The reference implementations are named the Partner Portal application and the Training Management application.
The Partner Portal application uses Microsoft Office SharePoint Server 2007. It shows how to create an extranet for companies who are partners with Contoso Pharmaceuticals.
The Training Management application uses Windows SharePoint Services (WSS) 3.0. It shows how to build a single intranet site. It is less complex than the Partner Portal application and demonstrates how to implement many basic SharePoint capabilities such as accessing lists and creating workflows.