Well, after some initial problems with the Article Submission Wizard, I have published a new article about a project that I have named Legion. Overall I am pretty pleased with this one.
The article can be found here.
While writing up a new article I noticed that there isn't a 'create new' Class Diagram option in the add new item dialog for a Silverlight project.
But, as I soon discovered, it's easy to create one. First create it in a regular Desktop CLR project e.g. a regular class library project. Then, simply drag it into the Silverlight project. Type may then be happily dragged from the Solution Explorer.
Now sharing types... no, we can't do that yet unfortunately.