I found this really "cool" recipe which I intend to try later this weekend:
Btw, I nicked it off from Fab Frugal Food.
BLUEBERRY MINT COOLER
8 cups water
1 pint blueberries
1/4 teaspoon salt
1 tablespoon lemon zest
1 cup lemon juice
1 handful mint leaves
Sweetener to taste*
Boil all ingredients except mint and sweetner for about 3 minutes, until blueberries have burst and are very soft. Strain liquid through a fine mesh strainer. Add mint leaves while liquid is still hot. Let cool to room temperature. Sweeten to taste. Serve over ice cubes. Serves 6 to 8.