Blackle (Like Google but black)
When your screen is white, be it an empty word page, or the Google page, your computer consumes 74 watts, and when it's black it consumes only 59 watts. A guy called Mark Ontkush wrote an article about the energy saving that would be achieved if Google had a black screen. Taking in account their huge number of page views, according to his calculations, 750 mega watts/hour per year would be saved.
In a response to this article Heapmedia created a black version of Google's search engine, called Blackle, with the exact same functions as the white version, but with lower energy consumption.
http://www.blackle.com/