MS has made available a preview of the Member Management Component that you can use to build into .Net 1.1 sample applications.  It isn’t exactly what will be released with VS.Net 2005, but it gives you something to play with so you can get used to the new model.

Be advised that it seems that it doesn’t seem to be licensed for production use.  If that interpretation is correct then it means that this is just something to play with in advance of VS.Net 2005 and can’t be built into any real applications.