Customizing SharePoint Context Menus
Drop-down menus in SharePoint enable actions that relate to a specific document in a document library. This article shows how these document context menus can be extended to add custom menu items.
Extensive article about visual mapping and information architecture in SharePoint environments.
A SharePoint research project from Stefanie Hain.
Real World Branding with SharePoint Server 2007 Publishing Sites
Extensive MSDN articles on branding and customizing SharePoint.