What does single sign-on mean to you (with ASP.Net examples)

While looking for sample code for simply cross-domain single sign-on for a new project, I stumbled across Micheal Morozov's excellent detailing of six different common meanings when someone talks about single sign-on. Better yet, he details the way that you setup ASP.Net web.config and code to accomplish each. Read Single signon for everyone for the details.