I'll second the Yogi teas. Over the winter, I'm constantly sucking down their Cold Season/Upper Respiratory Health mix. I've even found it at Safeway.

Last time I had a cough that lingered (that wasn't pneumonia) I used the otc stuff and it just didn't put a dent in it. Then, I decided to hell with it all and shared a bottle of wine with a girlfriend of mine and that seemed to do the trick. My face hurt like *hell* from the muscles finally getting to relax, but it seemed to be the turning point.