The Xfce 4 window manager manages the placement of application windows
on the screen, provides beautiful window decorations, manages work-
spaces or virtual desktops, and natively supports multiscreen mode.
It provides its own compositing manager (from the Xorg Composite ex-
tension) for true transparency and shadows. The Xfce 4 window manager
includes a keyboard shorcuts editor for user specific commands and
basic windows manipulations, and it provides a dialog for advanced
tweaks.

WWW: http://www.xfce.org/projects/xfwm4/