Brian Noyes just posted a set of Composite Extensions for WinForms which includes a working and very simple (see below) sample.
The sample illustrates:
It's great to see that Brian is investing the effort to give customers another way to build composite apps with WinForms. As Brian mentioned, we deliberately intended throughout the development of Prism to not unnecessarily couple any of the Composite App Library code to WPF even though WPF was our focus. That was a bit of a tightrope, which I'll discuss in a follow up post.
In the meantime, if you are building composite apps in WinForms, I recommend checking out Brian's post.