Use "lighter" programs - Software that takes up less hard drive space, and uses less system memory will keep the amount of writing and re-writing to the hard disk to a minimum, which will keep this vital computer piece in better shape. Also, programs which use less processing power to do the same work (like a simple text editor, verses Microsoft word) will use less energy in the long term.
Reuse hardware - Often, when companies upgrade their systems, perfectly good hardware can end up in the dumpster. If you consider the energy and materials involved in making a hard drive, or motherboard, then saving them from being junked can make a serious contribution.
Create "lighter" webpages - Websites are a great place to cut back on energy usage. Think about how much more processing power a flash animation uses than a simple text page. Then think about the thousands of people who could visit that site in a day. Obviously, high-powered content has its place, but this is still an interesting place to save some E.
Overall, greener computing is basically common sense. If it's harder for the computer, in memory usage, processing time, or website loading time, then it's probably using more energy. Once you see that, then you can save energy with your computer just like saving water with a sink. :: Nature Oriented Computing