Blackle Search 

Credit where it's due:

"Blackle saves energy because the screen is predominantly black. "Image displayed is primarily a function of the user's color settings and desktop graphics, as well as the color and size of open application windows; a given monitor requires more power to display a white (or light) screen than a black (or dark) screen." Roberson et al, 2002"

There's also an energy saving tips page! http://www.blackle.com/tips/

I'm off to watch old episodes of Captain Planet (with the brightness turned down :-)) - "Every little helps" is the phrase, I believe... :-)

Image courtesy of Wikipedia - http://upload.wikimedia.org/wikipedia/en/8/84/Captain.gif