sawfish.wm.ext.pager is a c/lisp extension that provides a functional desktop pager for the sawfish window manager. Originally written by Daniel Pfeiffer, it has been minimally supported since 2002, but still (somewhat) widely used. sawfish.wm.ext.pager is distributed under the GNU General Public License.
A pager is a map of your desktop. As maps go, it shows not only the visible part (your current viewport), but, if you are so configured, also the parts that extend beyond the sides of your screen. Also, if you have more than one workspace, the pager will follow you to where you are, or optionally show all workspaces at once. Of course you can select viewports and windows, and also move or raise/lower the latter.