Passive Solar:  A structure's ability to collect, store and distribute the sun's energy in winter (for heating) to block summer sun (for cooling) to greatly reduce additional heating and air-conditioning needs.  Passive solar design can be incorporated into any architectural style in any climate, but it requires careful site planning and selection of construction materials and building features.

A lazy woman's guide to passive solar, or ways to achieve passive solar gain when you're not building or remodeling:

In the summer, keep your curtains closed in the day time in order to block out light.

In the winter, keep your curtains open for solar gain during the day and closed at night.

Purchase a retractable awning or window treatments so that you have better control over solar gain during the day.

Use trees, shrubs, vines, and other greenery to ask as natural shades from the sun.

Other thoughts?  Post them in the comments section!