GNU & Linux Distros

Linux

Ubuntu: Linux for human beings™
Ubuntu is a Debian-based Linux OS that uses the GNOME desktop manager. Ubuntu is intended to be easy to use for beginners, but powerful enough for advanced users.


Fedora: infinity | freedom | voice™
Fedora is the consumer version of Red Hat Enterprise Linux OS. Fedora is used to test new features before they are integrated into Enterprise Linux. Fedora uses the KDE desktop manager.


openSUSE 11
The openSUSE project is a worldwide community program sponsored by Novell that promotes the use of Linux everywhere.


Gentoo Linux
Gentoo is a free operating system based on either Linux or FreeBSD that can be automatically optimized and customized for just about any application or need.


the slackware project
A no-frills version of Linux for serious geeks. Excellent for use on a personal server.


BSD

PC-BSD
A variation on BSD, a UNIX-like OS built by the Univeristy of California-Berkley. Uses the KDE desktop, and is aimed at the casual PC user.


FreeBSD
Closely related to PC-BSD, but supported by the Open Source community. Comes with both the KDE and GNOME desktops.


DragonFlyBSD
DragonFly is an operating system and environment originally based on FreeBSD. DragonFly branched from FreeBSD in 2003 in order to develop a radically different approach to concurrency, SMP, and most other kernel subsystems.


NT Clones

ReactOS
ReactOS® is an advanced free open source operating system providing a ground-up implementation of a Microsoft Windows® XP compatible operating system. ReactOS aims to achieve complete binary compatibility with both applications and device drivers meant for NT and XP operating systems, by using a similar architecture and providing a complete and equivalent public interface.