Here's a nice article on Federated Network Authentication by Matthew Gast on the O'Reilly Wireless Devcenter.
The article talks about
How can academic network administrators cope with the "roaming scholar" problem--that is, users having to use several guest provisioning processes to roam across wireless networks on a campus? This challenge applies outside the university setting too. Matthew Gast shows you how federated network authentication can make roaming easier for users and admins alike.