Thaw peaches, if frozen. Do not drain. Place peach slices, peach or apricot nectar, lemon juice, and cinnamon in a blender container or food processor bowl. Cover and blend or process until smooth.
If desired, reserve 2 tablespoons of the yogurt for garnish. In a large mixing bowl stir a little of the peach mixture into the remaining yogurt, stirring until smooth. Stir in the remaining peach mixture.
Cover and chill for 2 to 24 hours. If desired, garnish with the reserved yogurt, mint sprigs, and raspberries. Makes 4 side-dish servings.