This really only treats symptoms and does little to CURE the cold, but this herbal tea does wonders on a sore throat or a hacking, phlegmy cough.

Most of these supplies, including cheesecloth tea bags, can be found in many health food stores. All the herbs are considered edible so they very well may be carried there as well. If you can't find them there, check a local herbal shop or a magical supply store, who should either have them or be able to get them for you.

In a teabag, combine equal parts of: (I used one teaspoon of each. You can use more, don't use less.)
nettle LEAVES, not flowers (nearly any kind of nettle)
blackberry leaves
anise seed (more may be added for taste preference)
peppermint (more may be added for taste preference)

Boil water, pour over teabag and let steep for a few minutes until water turns dark. Sweeten with two teaspoons of brown sugar. Honey may be used, but the tastes do not blend as well. This is a fairly mild, sweet herbal tea which tastes a little like licorice if you like the stuff, and nothing at all like it if you don't. There is no strong herbal taste at all. Try emphasizing either the anise flavor, or the mint, if you strongly prefer one to the other. It feels much less soothing once it reaches lukewarm so if it cools off, reheat in the microwave.

If you choose, you may also add parts of sage, yarrow, chamomile, or catnip, but this will alter the taste unpleasantly if you use the first two--sage has a distinct taste which blends poorly and brewed yarrow is quite bitter. Chamomile will help you sleep easier, catnip has no strong effect but also soothes the throat.

This collection of herbs is good for soothing the throat, the steam can help clear out the sinuses, and also is good for breaking up phlegm, easing its expulsion.