First of all, it is certainly a good idea to put your model into a separate project. As you've discovered, this is trivial.
Regarding Controllers and Views, I don't see any obvious advantage to separating them for most basic projects, although you may have a particular need to do so in a particular application.
If you do choose to do this, then you will need to tell the framework how to find your controllers. The basic way to do this is by supplying your own ControllerFactory. You can take a look at the source code for the DefaultControllerFactory to get an idea for how this is done. Subtyping this class and overriding the GetControllerType(string controllerName) method may be enough to accomplish what you're asking.
Once you've created your own custom ControllerFactory, you add the following line to Application_Start in global.asax to tell the framework where to find it:
ControllerBuilder.Current.SetControllerFactory(new MyControllerFactory());
Update: Read this post and the posts it links to for more info. See also Phil Haack's comment on that post about:
ControllerBuilder.Current.DefaultNamespaces.Add(
"ExternalAssembly.Controllers");
...which is not a complete solution, but possibly good enough for simple cases.
Best Answer
Technically controllers are just .CS files that are put in the controllers folder and views are just .ASPX files that are put in the views folder. Your controllers classes need to inherit from the base Controller class and your ASPX page needs to inherit from System.Web.Mvc.ViewPage.
As far as getting those items in your menu though try opening your project file and replacing the projecttypeguids tag with this one.