First make the sugar syrup: Combine the sugar and water in small saucepan and boil over high heat until the sugar is dissolved.
Pour the sugar syrup into a 10 x 13 x 2-inch ceramic dish and stir in the orange juice, Campari, and lemon juice. Carefully place the dish on a level surface in the freezer. Freeze for one hour, rake the granita with a large dinner fork, and return it to the freezer. Rake the granite every 30 minutes, until it's firm and granular. This should take a several hours. Serve frozen in pretty bowls or stemmed martini glasses.