I had this project in which i had to create a web application that was actually a hosting system's panel. The users were in roles and the users were allowed to change the IIS configurations like add write permission directories, create websites, create virtual directories, create and recycle application pools, edit the default documents lists, create MS SQL server, enable coldfusion MX support, etc. All of these had to be done on the fly, i mean the user would be changing the actual system settings on the server that were allowed by the plan.

I used ADSI as an interface to IIS and this like helped me a lot

MSDN link to Programmatic reference to ADSI interface to IIS