Per Cabeza's request:
Hot apple cider is a wonderful thing this time of year. Mulled cider is even better.
Mulled cider is a descendant or perhaps a cousin of an older drink called wassail. Modern wassail is almost indistinguishable from mulled cider, but originally it was a beer or ale laced with citrus and other spices. The name wassail comes from Old English and Old Norse phrases meaning "be thou hale" and used as a greeting or a toast. It was enjoyed at Christmas, New Year's and Twelfth Night. It appears to have perhaps come from a Roman drink called calda which was a sort of diluted spiced wine traditionally enjoyed in the winter at Saturnalia festivals.
But whatever origins, mulled cider is a fantastic thing. Mulling cider should not be overly formulaic or prescriptive. It should be organic and should be able to respond to whatever whimsy happens to pass by at the moment. The general idea is to infuse cider (there's also mulled wine, but I've never tried it) with the flavor of some complementary spices, and usually, a sweetener is added.
The basic flavors are the spices associated with the holidays: cinnamon, cloves, nutmeg, and allspice. Other variations include cardamom, cranberry, anise, or some kind of citrus peel, usually orange. You get better and more pungent flavor from fresh whole spices as opposed to dried ground spices. Whole spices can also be more easily removed after their flavor has infused the cider. This can be an advantage because the ground spices tend to collect at the bottom of the mug as dregs. Folks sometimes use a teabag or a tea ball to counter the dregs effect, but I like to just run it through a fine mesh sieve. That way you still get some of the spices floating in there to give some texture, but you get rid of most of the bitter dregs. There are also commercial mulling spice mixes available, and some come in teabags, which are convenient.
The sweetener can be any sweetener. White sugar works, but is kind of bland. Brown sugar is a nice complement to the spices. Honey is mild but rich, and it is what I usually use. Molasses or a molasses/corn syrup mixture would give a deeper, richer hue to the flavor, but I've never tried it. I suppose melted caramel is another possibility, but I've never tried that either. My new and so far untested idea is to use maple syrup. Maple trees and apple trees are kindred autumnal images in my mind, and I think their flavors would also work well together.
So much for the basics. The method is pretty straightforward. You put it all together in a saucepan or a big pot and turn the heat on to high. You don't want it to boil because that can scorch the flavors, so watch it closely and just when it starts to steam, turn the heat down to low and let it steam like that for 20 minutes or so. It won't hurt it to go longer, and the longer it goes the stronger the flavors, but 20 minutes is usually sufficient.
A word about ratios: I usually do about 1/2 teaspoon each of ground allspice and grated nutmeg, eight whole cloves, and 2 cinnamon sticks to 4 cups cider and 4 tablespoons of honey. You can play with the ratios to emphasize the flavors you like better.
If you want to get fancy you can garnish it with a spiral of orange peel or cinnamon sticks as stir sticks. And you can top it with a dollop of butter or whipped cream, but I prefer mine straight. It is a great thing this time of year and at least through Christmas.