Install XFCE Desktop Environment on Ubuntu/Linux Mint

Xubuntu is a lighter version of Ubuntu that uses Xfce as the window manager. From the homepage: "Xfce is a lightweight desktop environment for various *NIX systems…"
Xfce is a lightweight desktop environment for UNIX-like operating systems. It aims to be fast and low on system resources, while still being visually appealing and user friendly.

XFCE Desktop Environment is really light environment, Ubuntu by default includes the Gnome desktop environment, but it’s easy enough to install another window manager. You can install XFCE desktop environment on Ubuntu 12.04/11.10/11.04/10.10/linux mint.

Installation of XFCE on Ubuntu/Linux mint, open Terminal and enter command:

sudo apt-get install xubuntu-desktop

Enjoy

Source: XFCE Website