Are there any best practices that cover the places that ASP.NET MVC models should be defined?
A new ASP.NET MVC project has a nice neat Models folder for them to go in, but in a production environment they can come from other places:
Is it acceptable for a strongly-typed view to use a class defined in such a location?
One issue that I've found is that, unless the model is defined in the web project, VisualStudio seems unable to find it when using a strongly-typed view specified in markup. My models are usually defined in a separate project and I've found that to use strongly-typed views, I need to create a codebehind so that I have a class that derives from a strongly-typed ViewPage. Then I change the markup and associate it with this class.
I don't know what you exactly mean by putting models in WCF services. If you mean using WCF services that expose the model object you need, that would work.
Regarding separate class libraries to hold your models, views and controllers, I think that's a pretty common approach and works pretty well. In fact, I believe this is really a requirement when the size and complexity of your application grows. It's a kind of physical separation of the distinct logical components in an MVC app.
In just about every project I have worked on the models of ASP.NET MVC are more View Models than models in the traditional sense of the word. I have yet to have a project where I can use the same Model that I use in my data access for my View Model. There is just too much other information that needs to be displayed on most pages. So for that reason I will either store my models in the models folder or store them in a separate library with all of my other MVC specific classes.
You need to import the namespace to the view page. This does not require a codebehind page.
Use the directive
<%@ import namespace='your.namespace.here' %>
immediately after the <@ Page..... directive