Save energy. Save the environment. Save money. Sounds good, huh? Savvy use of technology can help you do all three.

Stop overcharging your laptop battery: These days it's not uncommon for laptops to serve desktop duty. But here's the rub: If you leave the battery inside the system 24/7, it'll keep drawing power, even when fully charged. That's not only a waste of energy and money, but also bad news for the battery: Constant charging will reduce its capacity to hold a charge and its overall longevity.

Fortunately, there's a fast and simple solution: Pull the battery out. Most notebooks can run off AC power when there's no battery present, so take the latter out of the equation. It'll stay in pristine condition and save you a kilowatt or two. Estimated savings: A few dollars on your monthly electric bill and $120 on premature battery replacement.

Revive old PCs: PCs and landfills go together like oil and water--or, more accurately, like mercury (which can leak out of computer circuitry) and groundwater. Unfortunately, more and more unwanted computers and monitors end up in landfills every year, and the environmental impact is considerable.

Before you consign your unwanted system to the dump, consider giving it new life. One option: Wipe the hard drive and install a Linux-based operating system like gOS, which has such modest system requirements, it makes even a six-year-old Pentium 4 feel like a modern Core 2 Duo. With that done, the system could go to a student, a tech-challenged senior, or anyone with basic computing needs.

Alternately, an aged PC plugged into a router can double as a fine file and/or print server for your home network (see "Get More Out of Your PC"). If you're willing to spring for a TV tuner, you can install free media-center software like Media Portal and turn the old girl into a DVR--no monthly TiVo fees required. Estimated savings: $120 on a network-attached storage device.

Pay your bills online: Bills that arrive via snail mail represent a massive waste of resources (paper, printing, hauling, postage) on both the biller's part and yours, if you're still mailing back written checks. Maybe security concerns kept you from switching to electronic bill-pay services early on, but financial institutions have had plenty of time to work out the kinks, so there's no excuse for continued use of paper checks, envelopes, and postage.

Banks do charge for online bill-pay service, but some will give it to you for free if you do enough business with them. If not, take a look at MyCheckFree, which lets you pay many major billers free of charge. Alternatively, set up automated bill pay with the many utilities and banks that will happily collect their monthly fees, credit card, and mortgage payments via direct withdrawal from your bank account. Estimated savings: $40 a year if you can avoid electronic-payment fees.