Elderberry extract is great for the flu. How great? According to a placebo-controlled study from way back in 1995, nearly 90% of participants who took elderberry extract felt cured within three days. (Patients receiving placebo did not feel better until at least six days from onset of symptoms.)
Find elderberry extract at your local health food store or from a naturopathic doctor. It may be called Sambucol, Sambucus, or something similar.
Abstract: Inhibition of several strains of influenza virus and reduction of symptoms by an elderberry extract.