For colds, zinc lozenges that you suck (despite the questionable metallic taste) are great for pain of sore throat. The zinc actually prevents the virus from replicating. Suck one every 2 hours - up to 5 of them per day. But only do this for a few days as daily doses of zinc can lead to too high levels of it.

In the US, there is a product called Zicam which is zinc to be sprayed in the nose to kill the virus.

Extra Vitamin C prepares the immune system and helps fight the cold/ flu if you get it.

Oscillococcinum (O-sill - oh -koh- sign- um) taken at the first sign of the flu can bash it away. Get it at health food or herbal medicine stores.

There are also various "flu buster" or "flu preventive" things at herbalists.