CentOS -- Community ENTerprise Operating System is a free rebuild of source packages freely ailable from a Prominent North American Enterprise Linux vendor.

Super-fast and great-looking, Ubuntu is a secure, intuitive operating system that powers desktops, servers, netbooks and laptops. Ubuntu is, and always will be, absolutely free.

Debian GNU/Linux is a free distribution of the GNU/Linux operating system. It is maintained and updated through the work of many userswho volunteer their time and effort.

openSUSEopenSUSE 是一个自由的、基于Linux的操作系统，适用于您的个人电脑、笔记本电脑或服务器。您可以畅游网络、管理您的电子邮件与照片、办公、欣赏视频与音乐。

For the community, by the community, Linux.com is the central source for Linux information, software, documentation, how-tos and answers across the server, desktop/netbook, mobile, and embedded areas.

Red Hat is the world's leading open source technology solutions provider with offerings including Red Hat Enterprise Linux, open source applications, security and systems management, virtualization, Services Oriented Architecture (SOA) solutions.

Comprehensive information and resources about the Linux Operating System.