Writing custom providers without the overhead of Enterprise Library
Whatever you say about the the configuration functionality of Enterprise Library, one thing that won't be said is that it is straight forward. In fact, they created the Application Block Software Factory to help you through the five classes necessary to create the runtime configuration classes and a whole other set of classes for the design time experience.
Developers of small or local frameworks may not be willing to tie themselves to that horse just to set a few values in their web.config file.
Of course .Net 2.0 introduced the Provider Model, embodied in the System.Configuration.Provider.ProviderBase class. Unfortunately it's rather low on the workability scale itself.
This blog entry, by Phil Haack, shares a small generic library that will lower the bar to entry for making custom providers.