I hear a couple different things other people swear by for preventive and curing cold treatments:
Airborne (I have chewables--is the original drink powder better? I need to stock up on whatever works best)
Nyquil/Dayquil (syrup, not tablets)
Alkaseltzer (fizzing tablet)
Here are a couple unique ones:
baking soda/cider vinegar "tea"
What do you rely on for preventing and killing your colds?