Foods are separated into various categories such as 'carbohydrates' that include milk, fruit, vegetables, and starches. Foods within each category are easily 'exchanged' with each other to provide variety and personal choice. Portions of each food are specifically regulated to control calorie, protein, carbohydrate and fat content. A typical daily menu would look something like this: Breakfast: 2 grains, 1 milk, 1 protein; Lunch: 2 grains, 1 milk, 2 proteins, 1 fruit; etc. 

Good points:

Food exchange plans provide a flexible structure that allows numerous food choices. They typically are based on sound nutritional principles that provide adequate amounts of most nutrients. These plans can be easily followed for life, allowing long-term weight maintenance. 

Bad points:

Weight loss is typically slow and gradual. Food exchange plans require you eat foods from every food group, even if you don't like vegetables. 

Duration: Indefinite 

More information about this diet:

Check out the USDA Website for information on the Food Pyramid. 
http://www.usda.gov

You an eat at restaurants and alcohol and caffeine are allowed.  It is a diet that vegetarians can live with.