Exensible application shell for Windows Forms

We're about to start development of an in-house WinForms app (no WPF here), and I'm looking for a kind of an extensible "shell" application, which would take care of all the low-level stuff like menu & toolba开发者_运维问答r management, dialogs, etc. Pretty much like Visual Studio Shell:

What it should do is to allow us to write some kind of "add-ins" which would use services provided by this "shell" and do all the business stuff.

How about Composite Application Block?. Check the examples on the Internet, and see if that is what you want. It is not really a app. shell but more of a architecture to build complex app around; but the notion of application shell and loosely coupled parts are main theme in CAB (check Event Dispatcher among other things)