CentOS -- Community ENTerprise Operating System is a free rebuild of source packages freely ailable from a Prominent North American Enterprise Linux vendor.
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.
FreeBSD is an advanced operating system for modern server, desktop, and embedded computer platforms. FreeBSD's code base has undergone over thirty years of continuous development, improvement, and optimization.
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.
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.
