I use this at my church... (Score 1)

When researching for the same setup, I came across this: http://www.intellinet-network.com/en-US/products/9236-guestgate-mk-ii . We have a very large building, and trying to provide any kind of technical support to anyone who might possibly need it would be impossible, so encryption with a key was out of the question. For us, the main point of the capture portal is to keep people from driving by and using our internet connection. I basically use the Guest Gate because it provides a catch-and-release portal, but its internal DHCP server provides also each client with an IP on a different subnet (a little bit of security there). I couple it with Netgear access points that have client separation enabled so no two wireless clients can talk to each other. The Guest Gate has some rudimentary web filtering, but I wanted something a little more granular so I installed a Linux proxy with white/blacklisting capabilities outside of the portal. Now I can manage some content, and when guests or church members want internet access, I just need to give them the password for the portal. By the way, this setup is connected directly to the dual-WAN router and the router's firewall is setup so that none of the traffic on the wireless network has access to the internal network. The church staff can't access any internal network resources over the wireless network, but they've pretty much been content to have access to the internet itself. It's probably not the cheapest or easiest solution (unless you used the Guest Gate by itself), but it does exactly what I want, and everyone seems to be happy.