How about everything :)!

1. Integrating a Custom Snap-in Extension
2. Developing with Resources
3. Using Pup to Package and Unpackage Custom Resources
4. Custom Module
5. Web Services
6. CS core Systems
   • Catalog
     • SetJoinTable API
     • Customization and Extensibility Virtual Lab
   • Profile
     • Extending the Profiles System 
     • CSOLEDB
     • Profile Integration and Extension with Commerce Server 2007
   • Orders
     • Extending the Orders Runtime
     • How Do I Extend the Order System?
   • Marketing
     • Developing with the Commerce Server 2007 Marketing System
   • DWA
     • Commerce Server Data Warehouse
     • How to extend the Data Warehouse to include a custom Commerce Server event (Part 1)
     • How to extend the Data Warehouse to include a custom Commerce Server event (Part 2)
     • Learn how to extend an existing Data Warehouse class
     • Creation of a new Data Warehouse class
     • How to add a multi-value Data Warehouse class member
7. Partner SDK
   • Microsoft Commerce Server 2007 Partner Software Development Kit (SDK)
8. BizTalk Adapters
   • Schemas for Commerce Server 2007 BizTalk Adapters
   • Commerce Server 2007 BizTalk Adapters In Action
9. Starter Site
   • Architecture and Development for Commerce Server 2007 Starter Site: Click Here to View Recoding
10. AzMan
    • The "Customization and Extensibility Virtual Lab" will show you how to extend the AzMan.