Ubuntu

Ubuntu is a community developed, linux-based operating system that is perfect for laptops, desktops and servers. It contains all the applications you need - a web browser, presentation, document and spreadsheet software, instant messaging and much more.

http://www.ubuntu.com/getubuntu/download

Desktop Edition
* Ubuntu 7.04 - Supported to 2008
* Ubuntu 6.06 LTS - Supported to 2009

Server Edition
* Ubuntu 7.04 - Supported to 2008
* Ubuntu 6.06 LTS - Supported to 2011