Unless you plan to bike across the Western Hemisphere or swim to Europe or Asia, you'll likely burn fossil fuels on your summer vacation. But you can offset your carbon emissions by paying a little extra to travel. Carbonfund.org allows you to choose a category—car, plane or home—to mitigate your emissions. Travelocity.com offers a link to the Conservation Fund's Go Zero program, where you can offset your carbon load by paying for the fund to plan a native tree. Click on terrapass.com to estimate your carbon load for different modes of transportation. For example, a 2003 Honda Civic with manual transmission emits 6,710 pounds of CO2 annually. For $40, that amount will be offset by funding clean energy from sources such as wind farms and methane capture facilities.