I've often mentioned energy efficiency as one of many kinds of sustainable energy. The Sierra Club has just made a very nice site on their Global Warming and Energy site called Energy Efficiency: Cleaner, Faster, Cheaper.
My husband and I have been trying to be as energy efficient as possible, installing Energy Star appliances when others break down, and in case of the refrigerator long before, because old refrigerators (not even really old ones, use loads more energy than new ones. The new air conditioner a couple of years ago was the super-saver. That, and driving hybrids and turning of lights, and having all my computer things collected on a strip that I turn off at night, etc.
Read their page. I'm sure you'll find an idea you can use, too.