Microsoft.SharePoint.ApplicationPages

So you want to create a silk-layed-out SharePoint Administration page? Then you need to reference the Microsoft.SharePoint.ApplicationPages.dll!

Problem
I was looking for the Microsoft.SharePoint.ApplicationPages assembly, but I couldn't reference it from the assembly cache. Apparently it isn't begin installed in the assembly bin, but in the _app_bin of your web application.

Solution
You can create a (web app undependent) reference to the dll from the following location:
SharePoint 2007: 12-hive\CONFIG\BIN
SharePoint 2010: 14-hive\CONFIG\BIN