Not owning an ice cream maker is no barrier to making ice cream or a delicious dessert that resembles it.
This technique is similar to making a granita: A custard base is frozen in a shallow container and beaten every half hour to break up the ice crystals, until it is fully frozen. "I followed this recipe and it was awesome!" raves Rocky Road.
Frozen creams have a texture similar to ice cream. jmnewel makes a lemon cream that is nothing more than heavy cream, sugar, lemon juice, and zest stirred very well until the sugar dissolves and frozen in a baking pan. "It is delicious!" he says. "Creamy, but not airy like a mousse. There are no crystals of ice, unless you let it sit around in the freezer for a few days."
NameCake calls this recipe "super, super easy": Beat 2 cups whipping cream with 1 to 2 cups powdered sugar, to taste, and a pinch of salt until stiff. Fold in 1/2 to 1 cup chocolate sauce ("enough so that every bite will have several layers of chocolate, but little enough so that you can still clearly see streaks and layers of darker chocolate mixed in with the whitish-tan cream," says NameCake). Freeze, covered, 2 to 4 hours, or until solid.