The 2 that I know off the top of my head are Tomizone and Zappie. There are some more but there names escape me.
You can also run one your self DD-WRT have the option to tie into a radius server but you will have to deal with payments etc. They also have the option to integrate with some other solutions but they are mainly eu based.
At the end of the day they all offer different things. If you want to offer payment via the login screen and/or print off tickets.
Tomizone has payment via the website but you have to ask them about print off tickets and they will want to take a cut.
Zappie and Zenbu both offer tickets and online payment and wont take a cut from the printed tickets. Zappie will let you flash your own router but Zenbu will only allow you to buy a router pre flashed from them.
If your not to fussed about online payments and you want to try something that you control that is more complicated to set up then you can go down the DD-WRT route.
Surfspot, Voila, Hospitality Internet, Site Kiosk, SmartPay, Global Gossip, IAC [Internet Access Company], Mai wifi, Zappie, Tomizone [as mentioned already], Cafenet, Cybercom, Netstop, Chillifire, HQWiFi [in Queenstown] and others that I can't think of right now. Hot-spot.co.nz has apparently stopped service.
If the request was for wifi providers for users to connect to, there are swarms of them. If the request was for supplying a wifi system for the person to install at their premises to manage public service, not so many.
Some wifi providers fraudulently claim to be able to stop copyright infringing material, but that's not the case for users who know how to get around blocks. Fortunately, so far, there are have been few cases of copyright infringement brought, though the Kim Dotcom raid and illegal and disproportionate attack on his business was a spectacular warning of what can happen to people providing internet services to the public.
It is notable that the government does not consider themselves guilty of aiding and abetting crime by providing roads on which burglars can conduct their operations, but they expect information superhighway providers to be able to stop Cyberspace burglars and will levy $10,000 fines on people innocently providing internet connection to customers.