GPS units
Hate to stop and ask for directions? The global positioning network, a constellation of two dozen satellites, orbits high above the earth, recording precise data on your location and where you're headed. Using the satellites is free, but you'll need to pony up between a few hundred and a thousand dollars for the receiver and digital maps. "If your job requires you to drive to new and different places," advises Marzen, "buying a handheld or dashboard GPS unit is deductible as a way of getting from here to there quickly and efficiently."

If you already have a notebook, you'll need an external GPS receiver and mapping software to go with it. Regardless of whether you want your GPS setup to get you to your next sales call or your family's summer road trip, it'll put you on the right track.