Internet Access at your Local Libaries?

gettingOnline asks: "I work for a library that will soon offer public access to our network. You come in with your network ready portable computer, change your config to use DHCP, plug in, and you have T1 access to the net. Other libraries are offering this service already, and there's no doubt we will offer it, no matter what the security issues are. What I want to know from all of the network gurus out there is what we can do, short of creating a separate network, to minimize risk without limiting internet access."