To do so, open the iPhone Configuration Utility (download), and create a new "Configuration Profile" with the following information: (Update April 2010: Peter Kroon pointed out to me that he had to select "WEP" instead of "WPA/WPA2 Enterprise" - so if the below settings do not work for you, try WEP):
Don't forget to also set your username in the "Authentication" Tab (e.g., p12345678@staff.rug.nl), and copy the configuration profile to your iPod/iPhone which should appear under the Devices seperator in the sidebar.
That should do the trick.