Our History Dept. chair asked me about Blackle today. I'd never heard of it, but did some digging. Apparently, an all-white page background (such as on Google), eats up the kilowatts. An eco-blogger calculated that if Google switched to a black background, it would save the equivalent of $75,000/year in energy. That's not chump change.
So Heap Media created Blackle using Google Custom Search, which uses a black background. Of course, once you go to the actual website, it displays as it normally would. Surprisingly, I found the dark background MUCH easier on the eyes, so maybe it's not a bad idea.
Cool to realize that I created an eco-friendly blog without even knowing it!