PreparationFor Blueberry Sorbet: Combine all ingredients in medium bowl. Let stand until berries thaw and sugar dissolves, stirring occasionally, about 2 hours, or cover and chill overnight. Transfer mixture to blender or processor. Blend until mixture is smooth but specks of blueberry are still visible. Transfer to ice cream maker; process according to manufacturer's instructions. Spoon sorbet into container. Cover and freeze until firm, at least 3 hours. For Grapefruit Sorbet: Using knife, cut peel and white pith from grapefruit. Working over bowl, cut between membranes to release segments. Squeeze any juice from membranes into bowl. Discard any seeds. Cut each segment into pieces; add to bowl. Transfer contents of bowl to 4-cup glass measuring cup. Place 3 cups grapefruit and juice mixture in blender (reserve any remainder for another use). Add 3/4 cup plus 1 tablespoon sugar and vodka. Blend until almost smooth and sugar dissolves, about 2 minutes. Taste and add more sugar by tablespoons, if desired; blend to combine. Transfer to ice cream maker; process according to manufacturer's instructions. Spoon sorbet into container. Cover and freeze until firm, at least 3 hours. (Sorbets can be made 1 day ahead.) Arrange 1 scoop of each sorbet in dessert goblets. Garnish with fresh blueberries and grapefruit segments, if desired.