The ASP.Net Developer Center on MSDN has thrown up another useful article - or actually a pair of articles - on the Provider pattern.
In this first article, Rob Howard describes how the Provider model is implemented in .Net 2.0, along with a worked example.
Providers are, to my mind, absolutely central in developing flexible software architectures - being able to "unplug" a default provider and/or "plug-in" your own replacement/extension is central to role management in .Net 2.0. But it's also a very useful pattern in it's own right. The Search engine I wrote as part of the Mando Common Platform uses exactly this pattern (although partly configured via a database as well as via the web.config) to allow "pluggable" search handlers to operate across a variety of data sources.
But what's more interesting is that in the second article, Rob provides a parallel implementation of the provider pattern in .Net 1.1 - in the process clearly explaining how the pattern can be implemented in .Net 1.1.
This pair of articles really should be required reading at Mando for the programming team!