They must be the first for others to show the way, no big deal. They have included support for Windows CardSpace while signing in to Windows Live Mail. You need to have IE 7 installed as well as .Net framework 3.0.
Clemens Vasters wrote two days ago about it. However, his post is less than what I call short and short on many accounts because no one tells you that in order to use it from non-administrator accounts, you need to add the two certificates IE 7 shows you (one issued by Microsoft to Windows Live Mail, and the second one issued by Verisign which verifies the Microsoft’s certificate) to your trust store before Windows CardSpace launches successfully.