Walk instead of drive
You may find that you can walk faster than you think. I have found that it is pretty easy to keep a 3-4mph pace without breaking a sweat. If you have to go somewhere that is only 1 mile away, it will take you about 15-20 minutes to get there.
Compare that with spending a few minutes grabbing your keys, climbing into the car, starting it up, pulling out, driving through traffic, parking, and finally climbing out of the car and locking the doors. Your car typically gets the worst gas mileage and pollutes the most when it is cold. One mile is not sufficient to warm up your engine in the least.
Walking has other benefits other than just saving you money and polluting less. Walking is one of the most efficient ways to metabolize body fat. If you have a one mile commute, consider walking as a substitute to driving at least a few days a week. The rewards are plentiful!