Modern desktop environments make it possible for you to work on several
documents in several windows at the same time. This will inevitably result
in lots of open windows on your desktop.

Switching between applications can become a real pain: the buttons in the
taskbar already got too small to be usable, and finding the right window in
the tablist takes ages.

expocity is an effort to integrate an efficient means of switching between
applications into the window manager metacity, similar to Expose(tm) on
Apple's OS-X.

Use ALT+TAB to switch between application.

WWW: http://www.pycage.de/software_expocity.html