The popular window grouping and manipulation applet DockBarX
has added support for live
window thumbnails – not unlike that offered in Windows 7.
It does this by making use of the KDE compatibility plugin available in Compiz, so users will need to have Compiz Config Settings installed to make use of this feature.
Full installation instructions, along with a comprehensive guide to DockBarX’s many, many button configurations can be found @ gnome.look.org
Talika provides similar functions to DockBarX – including thumbnail previews using the Compiz preview plugin.