Check out the latest release of SharePoint Server 2007 SDK. Tons of sample code refresh, how do I... programming tasks, conceptual overview and most importantly developer tools and ECM starter kit is available in this SDK release.
If you are looking for customizing SharePoint Server 2007 or to extend feature available out of the box, this should be your primary resource.
Apart from the package feature like allowing you to choose the installation location, start menu navigation, there are some awesome additions:
There are additional samples on workflows, RM policies, content processing and some informative white papers. Download today. Hopefully this would enhance the ability to code and customize SharePoint Server 2007 to a greater extent.