zinc works well if you take it at the first sign of a cold. That's the active ingredient in Cold Eeze lozenges. Astragulus is supposed to boost the immune system. Personally I think a clean diet, a multi vitamin and plenty of rest is best.
Similar to what others have said : HUGE cup with some strong chai tea, a heaping spoon (or more) of LOCAL honey, half a lemon juiced, and a healthy bit of peach brandy. Not only is it delicious but it helps tons (and makes you drowsy enough to slepp if you put enough brandy in)
Other than that, yea to the hot and sour soup. Long hot baths, and spend the day in bed.
Garlic soup. Take a 3-4 cups of chicken broth, about half a head of garlic. Peel all the garlic, add to the chicken broth and cook with the lid on til garlic gets very soft. Add one beaten egg and some gratings of romano cheese. Eat - take some advil - go to bed.
I usually make myself a toddy like Marie K described, except fairly strong (1.5 shots in it), take ibuprofen, and put on warm jammies and go to bed. That'll make you pass out and if you sweat, it's good.