xubuntu is the low-power, small-footprint version of ubuntu (using xfce):
"Xubuntu is the newest official Ubuntu derivative distribution, using the
Xfce desktop environment and a selection of GTK2 applications. Its
lightweight footprint is well suited for low-end hardware and thin
clients. Xubuntu builds on the solid foundation of Ubuntu, with
world-class hardware support and access to a vast repository of
additional software.
=== On the Desktop ===

* Xfce 4.4beta1 including a more flexible panel, many panel plugins
and icons on the desktop
* Thunar file manager
* GDM desktop manager
* Gnome Office (latest Abiword and Gnumeric)
* Evince document viewer
* Xarchiver archive manager
* Xfburn simple CD burner
* Xubuntu System Tools for GUI system administration
* Firefox 1.5.0.3
* Thunderbird 1.5.0.2
* Package updates manager
* Graphical .deb package installer (''GDebi'')

* New documentation (''Xubuntu Desktop Guide'')
* New and more consistent artwork

and more.

In addition, OpenOffice.org and Gnome CUPS Manager are included on the
alternate CD but not installed by default."