Mullein is a non-psychoactive herb which can promote effective coughing (to clear you lungs), and absorbtion of material into the lungs. It is often used in smoking blends as a base because it burns very well and aids the absorption of active chemicals in the smoking blend into your lungs.
Mullein is available online, but it grows wild in many places. It is very commonly spotted along the side of highways and roads which makes it very easy to find.
Recently a new type of mullein has been discovered to be psychoactive, it is called Moth Mullein.