Authentication on an Untrusted Network?

PapaZit writes "I'd like to set up a wireless access point to simplify LAN parties and other social geekery. All of these people should have access to the network when I allow it, but not otherwise. The filtering and routing solutions that I've seen are all based on IP addresses (which can easily be faked, changed, or stolen) or WEP (which requires a shared secret and reconfiguration of all systems if the secret has to be changed). Would filtering on MAC addresses work? PPPOE? RADIUS? Does anyone have experience with Linux or BSD tools that do this?"