Don't use screen savers. Turn your monitor off instead, or configure your computer to automatically turn it off when not in use. Screen savers may save pixels, but they waste energy. Turning your monitor off saves both pixels and energy.
Turn your computers and monitors off at night, or between uses. It's not true that you'll damage your computer by rebooting it, but it is true that you you'll save a significant amount of energy.
It's time to replace those incandescent bulbs with CFLs, or compact fluorescent lights. CFLs use 75% less energy than incandescent bulbs, and can last up to 10 times longer. They don't buzz or flicker, and most turn on immediately. The color and quality of the light may take a few days to get used to, but the savings are worth it.
Use power strips for things like TVs, A/V components, video game systems, etc. When not in use, turn off the power strip to cut power to everything. Even when turned off, things like TVs consume power, so using power strips to control several components at once makes turning them all off much easier.