Komposť offers a great new way to manage a big number of windows on different Virtual Desktops.
Thanks to the KDE framework it is possible to create those screenshots "on the fly" while you are working without much overhead. The image scaling is done through the high performance image library Imlib2.
Since version 0.5 support for the Composite and Damage extensions has been added, which allows us to display window contents without grabbing screenshots. However with the current state of graphics drivers XOrg may be awfully slow (or even crash sometimes) when enabling the Composite extension.
Komposť is open-source software, licensed under the GNU General Public License (GPL).