wifi public access

[Jim Pazarena]

I distribute wifi internet to my customers via MAC
authentication at the access point, and DHCP assignment
from my server.

I would like to offer "wide open" (no MAC authentication)
at the access point, and have my server (somehow) permit
the access, or re-direct non subscribers to a sign-up page.

To provide service to the tourist traffic and non clients
on a pay-per-go basis.

What kind of software should I be looking for? It was suggested
that non-clients get routed to a specific point. How would I
accomplish this?

TIA

Jim