Enlightenment is one of hundreds of desktop environments available for Linux users. Although, more obscure than KDE and Gnome, there are still a number of distros which use this as the default desktop environment. Enlightenment's goals are an artistic experience with minimal system resources used.
A great strength of Linux, and open-source in general, is the number desktop environments available. For those who want something full-fledged with many utilities there's KDE and Gnome. Older computer users or those who just want to use less resources can go with XFCE and still have many of the benefits of the larger desktops. The minimalists use Fluxbox, LXDE, and Ratpoison where everything is set up by the user. However, with a sizable following, Enlightenment strives for a feature-rich yet visually stunning experience for the user.
Unlike Gnome or KDE, up until Enlightenment 17 (also known as DR17) it was only a window manager. However, DR17 has not yet reached a stable release. A major project, the E team is rewriting the entire code base but many distros still chose to go with DR17. As always with beta software, backup your data just in case. For those who want to try Enlightenment but worry about using a beta, DR16 is still maintained and is included on many distros.
Elive's slogan "Where Debian meets Enlightenment" says a lot about their goals and is one of the most well-known enlightenment-based linux distributions. At this time to download the stable 1.0 version of Elive requires a donation. Unstable releases are free. I recommend trying the unstable release first. The software in the 1.0 version is a bit dated- 2.6.18 kernel, version 2 of Iceweasel (Debian's version of Firefox), and Xorg 1.1.1. The software in the development versions is much more current. When the second stable release hits, it should definitely be worth checking out. It will be free to try too, with a charge only for installing. There are a few unstable releases- the general one, a release for Macbooks, and one testing out the effects of Compiz called Ecomorph.
Elive on Distrowatch
For those who value the simplicity that Ubuntu has brought to Linux, there's OpenGEU. Their current stable version, Luna Serena, is based on Ubuntu 8.10 which is slightly out-dated but still supported. The OpenGEU project seems to be basing their release schedule on Enlightenment more so than on Ubuntu, similar to Foresight Linux and Gnome.
I played with the Live CD, and it really is as pretty as the screen shots. There are two main themes, Sunshine and Moonshine. Choosing one completely changes the desktop from the window borders, widgets, and background. The distro uses a modified DR17 with some parts of Gnome to fill in the feature gaps of DR17 which are still in development. Abiword and Gnumeric are the default office applications instead of Open Office, and Claws is used for email instead of Evolution. The Ubuntu repositories are available for additional software and the OpenGEU team also maintains some of their own.
OpenGEU on Distrowatch
Yellow Dog Linux
A very different distro from the above two, Yellow Dog Linux is based on Red Hat Enterprise instead of Debian. The install DVD also includes KDE and Gnome in addition to the default Enlightenment so you can switch desktop environments. It also is compiled to run on the Power architecture and not Intel X86. Therefore, the official Red Hat repositories will not work with Yellow Dog since those programs are compiled for x86. Yellow Dog does maintain their own repositories. Historically, Yellow Dog was licensed by Apple to resell their computers with the Linux OS. With Apple now using Intel processors, Yellow Dog Linux has instead formed a partnership with Sony and IBM. Specific development has been done for Yellow Dog to run on Sony's Playstation 3 as well as a number of Sony and IBM server and workstations. Downloading the basic system is free, but advanced support with other benefits are sold through their website.
Yellow Dog Linux on Distrowatch
Yellow Dog Linux on Wikipedia
Yellow Dog Screenshots