It's here  on the "Learn Windows SharePoint Services" page.

Creating and Deploying a Feature Creating and Deploying a Feature
Step through the process of using Visual Studio to create a custom feature.   

Creating and Using Event Handlers Creating and Using Event Handlers
Create a list item receiver class to handle events.   

Creating Custom Document Information Panels Creating Custom Document Information Panels
Integrate Document Information Panels and content types in Windows SharePoint Services V3.   

Creating Custom Workflows with SharePoint Designer 2007 Creating Custom Workflows with SharePoint Designer 2007
Build a custom workflow using SharePoint Designer 2007.   

Customizing a Site with SharePoint Designer 2007 Customizing a Site with SharePoint Designer 2007
Understand the difference between page templates and page instances.   

Getting Up and Running with Excel Services Getting Up and Running with Excel Services
Publish an Excel spreadsheet to a Windows SharePoint Services V3 site.