Virtualmin is a control panel for Linux servers that allows site owners to manage domains and web sites and interact with server. It can be used in conjunctions with Webmin.
You can manage domains, email addresses, databases create and sell hosting accounts.
Allows to create and manage users, create virtual servers, edit/manage FTP users and databases, install scripts, change server settings, view logs and reports, create and restore backups.
Is similar in functions with popular cPanel application, allows you to work with server and your website domains through a graphical interface.
All features are included in free version, also they have a Pro (paid) version that offers 100 applications ready to install, interfaces for Ruby on Rails, Ruby Gems, Python, Django.