While working for WPF and Composite Application Library (CAL) for the first time, I had some difficulty both understanding their concepts and apply them in the optimal way, but I tried harder.
One of the benefits of CAL I found was the Command Binding which truly facilitates complying to the Model-View-ViewModel UI Design Architecture. But finding an easy implementation for them in all the desired control was not as easy as with default menu items and tool bars. A question on stackoverflow was asking about implementing the Command Binding with the WPF Ribbon which is downloadable within the WPF Futures, and not included in the out-of-box visual studio installation.
The trick was to make custom region adapters as those of menu and tool bar. I have found samples of RibbonRegionAdapter.
To comply with CAL and Model-View-ViewModel, the View containing the Ribbon will be be bound to a ViewModel containing all commands. These commands would be exposed publicly and available to other modules to attach Executed and CanExecute handlers. It is possible also to expose a generic method to add commands at run time by providing their image and location on the ribbon.
I found also open source implementation for binding the docking manager. The Composite WPF Contrib Project on CodePlex contains a TabGroupPaneRegionAdapter for Infragistics TabGroupPane.
Technical Thoughts 