There are few different Open Source operating system but the most common ones are distributions based on the linux kernel. Linux is registered trademark of Linus Torvalds.

The number of linux distributions is never ending. Since we are only talking about Desktop PCs and not servers I'll only mention the most popular desktop distributions.

The most popular Linux Distros at the moment are Ubuntu, openSUSE and Fedora. You can find the list and information about other Linux distributions on Distrowatch website. 

My personal favourite is an Ubuntu clone called Kubuntu but the current top of the list is Ubuntu which is the same operating
 system with different interface. The nice thing about K/Ubuntu is that if you have a slow internet connection or just want the original disc they will send you CD completely free (including postage). Order them here - Ubuntu CDs, Kubuntu CDs.

Most Linux Distros come with a complete set of applications for common tasks such as Office suite, instant messaging, image manipulation etc. There is virtually no viruses, spyware and firewall is built into the system and works without you even knowing that is there. If you are a fan of Eye-Candy you will love Linux as its customizable to infinity and beyond. For a good list of Linux Applications go here.

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