John Collins draws some nice attention to the ValueModel framework in VisualWorks:

ValueModel was part of their VisualWorks application. As far as I know, that was the most highly evolved MVC-oriented GUI application programming framework devised in Smalltalk.

If you download the Application Developers Guide and do a search on ValueModel - you will get treated to some nice diagrams and code. Not a lot, but they are the right ones to examine. There is a page with all the VisualWorks documentation, if you want to browse everything.

It really is a nice framework, and applicable (as John explains) beyond Smalltalk.