Ubuntu is a free, open source Linux Operating System based on Debian Linux. This flavor of Linux focuses on the User Friendliness and usability of Linux. In spite of being open source, Ubuntu team is dedicated to provide support at least for 18 months after a particular release of Ubuntu.
Also Ubuntu is the most preferred flavor of Linux in this world. And Ubuntu support both x86 and Sun sparc architectures. So that you can run Ubuntu even on Sun Hardwares. In order to increase the popularity, the Ubuntu team is giving away free copies of Ubuntu Linux either by download or by free CDs.
Don't get excited.. its true. They are giving away free CDs.
You can get it from here