Yeah, we have something similar to this on campus for our wireless network. The term we use I think is a "Captive Portal". When you start up your laptop with a wireless nic in it, it gets assigned an address through dhcp and seems to be connected. Then you open any web browser, and it redirects you to the (encrypted) login page where you give your uname/pass and after that it redirects you right on to the webpage you were actually visiting... It also opens up all the other ports on your IP, so you're not always going through an http proxy.

Our network at berkeley is called AirBears, and I'm sure google will turn up more information on what software they're actually using.

Matthew