uses WHM and WHMCS
WebHost Manager® (WHM®) provides hosting providers with a graphical interface to manage every account on a server.
With WHM® software, managers can configure Services, Deployment Package, Control DNS and FTP configuration, accounts, security settings, and more.
http://cpanel.net/cpanel-whm/Hands Free Automation
Automate everything from Account Provisioning to Domain Management to Email Reminders and more...
Domain Management
Buy, transfer, renew and manage domains in real-time without ever leaving your website - all transparently
Multi-Currency Billing
Multiple currencies, auto exchange rates syncing, up to 2 levels of tax rules and a fully multilingual client area
Fully Customisable
Fully templated, easily customisable, modular extensability, hooks and an API make extending and integrating easy
Integrated Support Tools
Built-in Support Tools including Announcements, Knowledgebase & a Fully Featured Support Ticket System
http://www.whmcs.com/