Lubuntu, Ubuntu with LXDE
The Lubuntu project has released the first test release of its Ubuntu based distribution that uses LXDE, the light weight desktop environment, as it's desktop environment. The Lubuntu developers are hoping to join the official Ubuntu family of Ubuntu with GNOME, Kubuntu with KDE and Xubuntu with Xfce, as an officially supported distribution after discussions with Mark Shuttleworth in February. To achieve their goal, they have become a self supporting project within the Ubuntu community. The Lubuntu project has a Wiki and Launchpad site for coordinating development.
The just released test version of Lubuntu is a 340MB Live CD image and is based on the in-development upcoming version of Ubuntu 9.10, Karmic Koala. The small size of the ISO image is not just down to the use of LXDE though; the distribution is also missing applications, such as office software.