There are many basic types of solar cookers, in a dazzling variety of configurations. You can build your own or purchase one of a variety of commercial models. There is a wealth of great information already on the web about these cookers, so there is a section at the bottom of thiis page pointing to a few of the many other sites that have already compiled detailed information. Our Duranago Renewable Energy Group held a solar cooker building party on June 30th, 2002, and experimented with a commercial model and a new type of cooker (as far as I know!) made from a recycled satellite dish.
This cooker is about 7 feet (2.1 meters) in diameter. It is constructed from a recycled satellite dish with strips of aluminum foil glued to its parabolic shape.
Members of the Duranago Renewable Energy Group pose with the partially completed satellite dish cooker after applying strips of aluminum foil.
Here's links to some other organizations offering information on building solar cookers: