WHMCompleteSolution
From WebHost Wiki
WHMCompleteSolution, or just WHMCS as it is known by its users, is a Client Management, Billing & Support System designed for Web Hosts. Integrated directly with server management software, WHMCS can provide your hosting company with high levels of automation and drastically reduce the time you spend administering simple tasks. Also, being completely template based along with modular components for gateways, registrars & servers makes it completely customisable & expandable to fit your needs.
