Noticed that people are already seeing this blog ... that is certainly interesting.
Different people learn in different ways. Some people learn by experimenting with a technology. Some learn by formulating different search queries to their favorite search engines. Some learn by watching others. I've always been one to learn by reading books. Books are different than KB articles. They typically are infused with the voice of a particular author.
In working on my last technology, Certificate Lifecycle Manager and Identity Lifecycle Manager, I didn't have the benefit of many written resources. What few I saw were:
The Active Directory Cookbook, 2nd edition http://robbieallen.com/blog/adcookbook/index.html which discussed MIIS.
Morimoto's Exchange Server 2007 Unleashed http://www.amazon.com/Microsoft-Exchange-Server-2007-Unleashed/dp/0672329204 has a good discussion of Galsync and also discusses some of the other MA's (Lotus Notes, I think).
Most of the resources were blogs:
Calderon's blog: http://blog.identityjunkie.com/2007/06/learning-microsoft-identity-management_04.html is a good source of the links needed to learn identity management.
However, in the ADSI/WMI space, there are lots and lots of written documents.
I started with the Kaplan and Dunn book, The .NET Developer's Guide to Directory Services Programming (2006), which does a fairly good job of explaining how to use the System.DirectoryServices namespace, and touches upon the System.DirectoryServices.Protocols namespace as well. My friend Tim MacCaulay, who is as crazy about books as I am, gave me a copy when we essentially switched teams (he's on the DSC-Identity team now).
The classic book about ADSI (which stands for Active [Directory Services Interface], not Active Directory [Services Interface] -- it can be used against many things other than Active Directory) is Simon Robinson's book, Professional ADSI Programming from Wrox Press (1999). My colleague Joe Cordero gave me a copy of that 800 page monster. Though there are a number of things in that volume that are quite dated, if you are writing a provider, and using ATL (the active template library), there really isn't a better reference. In my serious COM days, I used a lot of MFC (Microsoft Foundation Classes), and never really worked much with ATL, so having a good explanation was for me a must.
Another senior engineer here in North Carolina, David deGroot, used the Oppermann volume, Microsoft Windows 2000 Active Directory Programming (2001) as his vade mecum when he was on the ADSI team. If you are coming into an environment with lots of vbs scripts that perform all kinds of administrative operations, and you don't know a thing about writing VB Script code, this is the book for you.
Of course, for a variety of security reasons (I was at Microsoft during the http://en.wikipedia.org/wiki/ILOVEYOU virus epidemic), vbs scripts are often discouraged these days. Powershell scripts (which can be signed) are a better way to make ADSI calls. More on that later.