What you should do depends on if it's a simple cold (viral), or if you have had a cold and the inflammation & swelling has led to a bacterial sinus infection. With a regular cold I usually wait it out, haven't really experimented with potions and whatnot, although some of the above suggestions sound interesting enough to try next time I get a cold. But if your snot turns solid yellow and smells bacterial (kind of dough-ey, yeasty) then it's a sinus infection and you should embrace modern medicine and get some antibiotics. Amoxicillin should knock it out pretty well, and for me at least, won't make me <img src="/forums/images/graemlins/barf.gif" alt="" /> like erythromycin.