In a small bowl, combine raisins in rum and soak for at least 2 hours. Preheat oven to 350 degrees. Lightly coat a 10 by 3-inch round baking dish or 2-quart souffle dish with vegetable cooking spray. Add the bread cubes to the dish and sprinkle the raisin/rum mixture on top.
In a large bowl, combine the milk, eggs, sugar, cinnamon, and nutmeg. Stir the egg mixture into the bread/raisin mixture. Cover with foil. Place the baking dish in a larger, high-sided roasting pan. Add boiling water into the roasting pan around the baking dish to a depth of 2 inches. Bake for 45 minutes. Remove the foil. Continue baking, uncovered, for 5 minutes, until top is golden and the mixture is slightly puffed or until a knife inserted near the center comes out clean.
Cool slightly before serving. If desired, serve with Creme Anglaise, flavored with rum to taste, if desired.