Eduroam
Just the other day I discovered that my university, University of Oslo, had joined Eduroam. Eduroam stands for Education Roaming, and is a RADIUS-based infrastructure that uses 802.1X security technology to allow for inter-institutional roaming.

Universities around the world have set WIFI equipment for students/scientific staff can access the Internet from pretty much anywhere on the campus. The networks are most oftenly not open, and that is the case at our university also. To access our wireless campus network you need to authenticate with a username and password, something that often have been bad news for visiting professor, as it meant that they had to find someone with network permissions access, register as a user, and get a guest password before beginning work. Well, that could take most of their first day at the campus. This led to the start of an European consortium of network gurus developing a roaming solution allowing users of participating institutions to access the Internet at other campuses by using their credentials from their home institutions. A visiting researcher tells the local network where to go to confirm his or her credentials. Once confirmed, the network issues limited access based on pre-set controls.
A wide range of European nations have already joined the initiative, including the Netherlands, United Kingdom, Germany, Greece, Czech Republic, Spain, Portugal, Croatia, Slovenia, Denmark, Poland, Latvia, Finland, Norway, Luxembourg and Italy. Taiwan and Australia are examples of countries from outside of Europe that have also joined Eduroam.
The solution works with MacOS X, Windows and Linux (but configuring it for Linux seems close to a nightmare…).