Foxglove is also my favorite example of herbal remedies driving drug development... it's the central compound to the digitalis family of drugs for regulating the heart rate.

Interesting history on the foxglove/digitalis connection at
http://www.bris.ac.uk/Depts/Chemistry/MOTM/digitalis/digtalis.htm.
[Although "Molecule of the Month"? I think I'm going to vomit... ]