Ubuntu developed by Canonical Ltd - Ubuntu Foundation, The Ubuntu Team

Ubuntu is a free open source operating system focused on stability and ease of use. It can be run directly from a CD without modifying a computer and can easily be installed alongside Windows. Ubuntu provides free alternatives to most proprietary software, such as OpenOffice instead of Microsoft Office, Firefox instead of IE, etc. Ubuntu is based on Debian Linux, inheriting it's package management system. This means that all programs can be added or removed in the same easy way, and literally hundreds of programs are available for instant download and installation.