On Shaan Hurley's Between the Lines blog, he has posted links to 5 videos you might find useful:
- Introduction to the AutoCAD 2006 Workspaces
- Introduction to the AutoCAD 2006 CUI Editor
- Creating a Toolbar with the AutoCAD 2006 CUI Editor
- Creating a Flyout Toolbar with the AutoCAD 2006 CUI Editor
- Introduction to the AutoCAD 2006 Enterprise CUI files
I suggest you watch them in that order, rather than the order listed on Shaan's site.