Coming out of your Shell Part I

Over my career as a software engineer, I have learned that no matter what the requirements are, most web apps are made up of the same basic components. A few of these components include a site layout, menu system, configuration, user management, a security model and a data model. For some time now I have been interested in developing a “shell” application from which most of my new applications could be derived. This shell application would need to include these “core” components, and would serve as the foundation, from which the rest of the app could be constructed.
I have considered using a portal system such as Xoops (PHP) of .Net Nuke (VB). Both do meet the above described requirements, including user management and providing extensibility points known as modules. Unfortunately, I feel that the core is designed with the needs of the open source community in mind, not those of my clients. Additionally, as it is an “off the shelf” product, I doubt that I would be able to effectively understand the complexity and extend the core as needed.
It is my intention that this open ended series will document my quest to develop “my” very own “shell application”, one that can be adapted and continually enhanced. It will provide both a starting point and eventually I hope an iron clad core for all future web apps.