Xfce is the Cholesterol-Free Desktop Environment.
Xfce is a desktop alternative to the popular GNOME and KDE environments. It is a GTK-based environment, like GNOME. It emphasizes speed and small size over features, though it is much more feature-rich than a bare-bones window manager.
ArchLinux XFCE-Wiki-entry Good information on setting up XFCE.
XFCE-Look Themes, Wallpapers etc