In response to a friends challenge to make a solar cooker and prove it would work in the UK, the solar cooker shown below was built. Only scrap materials have been used, mainly based upon a piece of plastic mirror found in a skip. It is a box-type cooker with a central oven around which there is plenty of insulation. One side has a glass front and the mirrors channel additional sunlight into the box. The mirrors slope at approximately 45 degrees.
A potato and a carrot were cooked over the course of about 3 hours on a bright October day, with an average of approximately 90°C being maintained. More testing and data logging is required to see how well it performs.

Built-it Solar US list of solar cooker links
Solar Cooking Archive Sponsored by Solar Cookers International
Solar Cooker Plans Great list of plans for all types of solar cooker
Solar Cookers International Solar cookers in use around the world
Backwoods Home Magazine Box-type solar cooker plans
DR A. Kundapur Review of solar cooker designs on a slightly ugly looking website
Solar Oven Society
Solar cooking in Peru