Here's a list of some Linux Desktop Operating System distributions:

Source is Distrowatch

Ubuntu is a complete desktop Linux operating system, freely available with both community and professional support. The Ubuntu community is built on the ideas enshrined in the Ubuntu Manifesto: that software should be available free of charge, that software tools should be usable by people in their local language and despite any disabilities, and that people should have the freedom to customise and alter their software in whatever way they see fit. "Ubuntu" is an ancient African word, meaning "humanity to others". The Ubuntu distribution brings the spirit of Ubuntu to the software world.

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The Fedora Project is an openly-developed project designed by Red Hat, open for general participation, led by a meritocracy, following a set of project objectives. The goal of The Fedora Project is to work with the Linux community to build a complete, general purpose operating system exclusively from open source software. Development will be done in a public forum. The project will produce time-based releases of Fedora about 2-3 times a year, with a public release schedule. The Red Hat engineering team will continue to participate in building Fedora and will invite and encourage more outside participation than in past releases. By using this more open process, we hope to provide an operating system more in line with the ideals of free software and more appealing to the open source community.

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Linux Mint is an Ubuntu-based distribution whose goal is to provide a more complete out-of-the-box experience by including browser plugins, media codecs, support for DVD playback, Java and other components. It also adds a custom desktop and menus, several unique configuration tools, and a web-based package installation interface. Linux Mint is compatible with Ubuntu software repositories.

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The openSUSE project is a community program sponsored by Novell. Promoting the use of Linux everywhere, this program provides free, easy access to openSUSE, a complete Linux distribution. The openSUSE project has three main goals: make openSUSE the easiest Linux for anyone to obtain and the most widely used Linux distribution; leverage open source collaboration to make openSUSE the world's most usable Linux distribution and desktop environment for new and experienced Linux users; dramatically simplify and open the development and packaging processes to make openSUSE the platform of choice for Linux developers and software vendors.

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PCLinuxOS is a user-friendly Linux distribution with out-of-the-box support for many popular graphics and sound cards, as well as other peripheral devices. The bootable live CD provides an easy-to-use graphical installer and the distribution sports a wide range of popular applications for the typical desktop user, including browser plugins and full multimedia playback. The intuitive system configuration tools include Synaptic for package management, Addlocale to add support to many languages, Getopenoffice to install the latest OpenOffice.org, and Mylivecd to create a customised live CD.

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