Blackle.com, powered by Google Search, is Google’s “Black Google” energy-saving engine, “saving energy one search at a time.” It’s really very cool, and Google encourages setting it as your homepage (black works for me). There’s a blogpost that is sort of the wiki-esque on this reasoning how much energy is saved with the black screen. But the bottom line is, that every little bit helps - and it is just plain interesting to check out!