Ubuntu

Ubuntu has to be by far the easiest Linux based OS I have ever played with. Take a look at that screenshot. Its gorgeous! It takes less than 30 mintues to install on a decent computer and It comes with tons of applications (including OpenOffice, Firefox, an email client, the GIMP Image editor, and a wide selection of games), and best of all its free! Its very easy to use, and the GUI looks like its got references to the Mac OSX and Microsoft WIndows. But it looks like somebody finally actually sat down and figured out what needs to be in an OS. There is even a server version that comes with LAMP installed. Its perfect if you have a computer lying around missing an OS.