Architecture Suggestions / Recommendations For A Web Application With Sub Apps

I'm starting to plan an architecture for a big web application, and I wanted to get suggestions and/or recommendations on where to begin and which technologies and/or frameworks to use. The application will be an Intranet-based web site using Windows authentication, running on IIS and using SQL Server and ASP.NET. It'll need to be structured as a main/shell application with sub-applications that are "pluggable" based on some configuration settings.

The main or shell application is to provide the overall user interface structure - header/footer, dynamically built tabs for each available sub-app, and a content area in which the sub-application will be loaded when the user clicks on the sub-application's tab. So, on start-up of the main/shell application, configuration information will be queried from a database, and, based on the user and which of the sub-apps are available, the main or shell app would dynamically build tabs (or buttons or something) as a way to access each individual application. On start-up, the content area will be populated with the "home" sub-app. But, clicking on an sub-app tab will cause the content area to be populated with the sub-app corresponding to the tab.

For example, we're going to have a reports application, a display application, and probably a couple other distinct applications. On startup of the main/shell application, after determining who the user is, the main app will query the database to determine which sub-apps the user can use and build out the UI. Then the user can navigate between available sub-apps and do their work in each. Finally, the entire app and all sub-apps need to be a layered design with presentation, service, business, and data access layers, as well as cross-cutting objects for things such as logging, exception handling, etc.

Anyway, my questions revolve around where to begin to plan something like this application. What technologies/frameworks would work best in developing a solution for this application? MVC? MVP? WCSF? EF? NHibernate? Enterprise Library? Repository Pattern? Others? I know all these technologies/frameworks are not used for the same purpose, but knowing which ones to focus on is a little overwhelming.
Which ones would be the best choice(s) for a solution? Which ones work well together for an end-to-end design? How would one structure the VS project for something like this?