YFi Hotspot Manager is a modern AJAX Web front-end for FreeRADIUS 2.x. It has support for vouchers, permanent users, billing post paid, and pre-paid. Multiple languages are supported. Statistics can be generated. It works with CoovaChilli and Mikrotik. It runs on Ubuntu and CentOS. It has Google Maps integration. Third party systems can be integrated. There is thorough documentation.
Kattive is a captive portal with an interesting interface, written in Perl and completely Web-based. It interacts with iptables or whatever you want. It's template-based. It works as a transparent rule activator and as an Internet Point interface. It has many features like schools/classes administration. If used in a hotel, you can count the time for billing.