There are 2 types of OTC cough medicines: antitussives and expectorants. A common antitussive is dextromethorphan (some brand names:
Triaminic Cold and Cough, Robitussin Cough, Vicks 44 Cough and Cold). The only expectorant available in OTC products is guaifenesin (2 brand names: Mucinex, Robitussin Chest Congestion).