For anyone who is into Mikrotik gear, they now (as of a couple of weeks ago) have a web-based user and billing manager package to compliment their hotspot solution in RouterOS. It looks like it is RADIUS based so can provide centralised management to multiple RouterOS based access points or routers.
After a bit of moaning from myself and others they have also pushed out a MIPS version for use on RouterBOARD 100/500 series which makes for a pretty decent embedded hotspot solution and is damn easy to set up. It is also relatively simple for people to add users and print tickets for over-the-counter use.
It is in beta stages so expect bugs (it doesn't work in IE7 yet for example) but so far things look good. The documentation is practically non-existent so I will post a tutorial on my website eventually. There is a basic one at http://wiki.mikrotik.com/wiki/MikroTik_User_Manager