Blackle.com is an energy-saving search engine offered by the Australian group, Heap Media. From their site:
"Blackle saves energy because the screen is predominantly black.... In January 2007 a blog post titled Black Google Would Save 750 Megawatt-hours a Year proposed the theory that a black version of the Google search engine would save a fair bit of energy due to the popularity of the search engine. Since then there has been skepticism about the significance of the energy savings that can be achieved and the cost in terms of readability of black web pages.
"We believe that there is value in the concept because even if the energy savings are small, they all add up. Secondly we feel that seeing Blackle every time we load our web browser reminds us that we need to keep taking small steps to save energy."
Blackle encourages you to use their site as your home page, for energy saving, and also offers a nice list of energy-saving tips, too.