This is a picture-pretty first course for a summer meal. Make in advance and serve chilled.
Cut cantaloupes in half. Remove seeds. With a spoon or melon baller, remove fruit from flesh. Refrigerate rinds to use as soup "bowls." Put melon into blender with sour cream. Blend to a creamy consistency. Refrigerate for at least an hour to chill soup and let flavors blend. Pour soup into melon bowls and swirl in a teaspoon of sour cream as a garnish.
Each serving contains approximately 129 calories, 28 g carbohydrates, 3 g protein, less than 1 g fat, 111 mg sodium, and 3 g fiber.