i have smoked all kinds of herbs. mullein and chamomile cig makes a great pre-bed ritual and is very relaxing. i used to smoke ephedra, when it was available, as a natural alternative to coffee. this was all in a "former" life and i have forgotten all the wonderful things i smoked. i don't think one herbal cig a day is bad. too many will inundate the lungs with smoke and particulate matter that is not good, but herbal cigs are not smoked compulsively like tobacco cigs are anyway.
gingko and go tu cola can be smoked if you need your brain reved up. i have done no research on this, this is all just my personal experience. i don't smoke anything these days, i am a clean living boy in my current incarnation!