When you wake up at 3 a.m. with the sort of sharp pain only prescription drugs can handle, head for one of the 24-hour Walgreens listed above. And even if you aren't in need of round-the-clock Vicodin service, it's a comfort to know that there are other human beings up and about at this time of night, stocking shelves and buying hair-care products and getting a quick fix of perfunctory human interaction. This is the place to come to carbo-load on cellophane-wrapped muffins for an unexpected all-nighter or to work off your insomnia with a stroll through the exhaustive candy bar section. Walgreens is also invaluable when you realize that you haven't done your holiday shopping yet and it's 4:30 Christmas morning.