Hi
if you like dark desktops/dark windows (skinned) you have to try this software:
Stardock Window FX.
Focus on the active window by darkening inactive ones
I'm using it since abou 3 years. You can darken all windows in the background
and also your desktop (with all icons). So if you have a dark wallpaper and dark
skins for all your applications then it's really relaxing to work the whole night with
your big 27'' monitor or sit with a laptop in front of a large TV-screen.
....a second feature ("Transparency"):
Enhance windows management (Transparency, size, roll-up) with right-click options
....you can adjust the transparency of all windows (focused and in the background): its also a
quite relaxing feature for the eyes.