Carbon-free, that is, by neutralizing your emissions through reforestation and renewable energy projects. Sites like the Carbon Fund help calculate how much CO2 your trip produces based on distance and type of vehicle. Look for airlines that offer passengers the option of tagging on the price of an offset to their ticket. British airways, for example, passes the money on to Cliamte Care, an organization that invests in sustainable energy in developing countries.

Cruise ships are much like floating cities, and they produce as much sewage and solid waste. If you must have your cruise, then scout out the ones that are making an effort to go greener through recycling and efficient waste water management.

According to the International Ecotourism Society, tourism is the 2nd most important source of foreign exchange for 40 of the poorest countries. To ensure that those dollars are spent in ways that promote conservation and social development, check out the Ethical Traveler's list of Best Destinations (www.ethicaltraveler.com). Belize, Costa Rica and Slovenia are among those that earn high marks.