if you want to avoid shopping at irresponsible companies...
Get out and walk
More than a quarter of US car trips are one mile or less, and 13.7 percent are a half-mile or less. For most of us, these are walkable distances. Find a backpack or briefcase on wheels that can tote your work items and laptop. For shopping trips, invest in a sturdy shopping cart or collapsible crate on wheels.
Bicycling is an excellent way to minimize car use and get exercise at the same time. Mounting wire baskets or pannier bags to your bicycle can extend your number of destinations by allowing for greater cargo transportation.
One way to go further without a car is by investing in an electric bike. With a range of about 20 miles between charges, electric bikes can be recharged from any standard household electric socket.
Also, 'sport utility' bikes allow you to expand your bicycle's cargo limit to the point where you can carry items as large as kayaks or luggage for a trip. You can find electric bikes, sport utility bikes, and bike enhancement kits in the National Green Pages™.
Check out Better World Club -- the nation's only roadside assistance service for bicycles as well as cars. And it is more eco-friendly than AAA.
Coordinate with your coworkers and neighbors to take joint trips to the office or shopping center. In metro areas like Washington, DC, and San Francisco, innovative carpoolers have even established “slug lines” -- areas where commuters can line up in suburban Virginia and catch a ride into the District of Columbia with drivers who were going there anyway. It's a free, grassroots bus line that also builds community.
Another way that people can share cars, and even eliminate car ownership altogether, is to take advantage of fee-based car-share programs like Zipcar (which now owns Flexcar). Members of these car-sharing programs take advantage of cars placed throughout participating cities, paying by the hour in order to run errands for which biking or bus-riding might not be practical.
Hop on the bus
Many cities that don't have extensive subways or other public transportation systems nonetheless run bus lines that often go underused by citizens used to driving their cars. Get a transit map from your local bus line and resolve to take the bus once a week to someplace you would have ordinarily driven. You'll experience your city in a new way, save energy, reduce pollutants, and perhaps even multi-task if you bring a book or a project with you.
If you must own a car...
Buy a hybrid
Most of the major car manufacturers now offer at least one hybrid car. But remember, not all hybrids are created equal. Check out HybridCars.com to learn more about the hybrid cars on the market.