"The beauty of eco-travel is that it's really as much about where you go as the decisions you make while you're there," Dorfman says.

"Eco-adventure" vacations, which give travelers the chance to learn about ecology firsthand, are growing in popularity. But if hiking through the virgin cloud forests of Costa Rica isn't for you, consider staying closer to home. Traveling a short distance by car or train is greener than flying, and once you start doing some research, you'll be amazed at how many cool attractions are right in your backyard.

Visiting a nearby state or national park can be a fun weekend getaway and a great educational experience for kids. And don't overlook major cities, most of which offer not only diverse cultural attractions, but also convenient public transportation systems that make it easy to get around without a car.