"Although the hallucinogenic properties of Salvia have long been known to the natives of Mexico's Sierra Mazateca range, it wasn't until the middle of the last century that anthropologists and drug researchers learned of the herb.
The substance is still legal in all but eight states, and it's openly sold in smoke shops and via the Internet. Just run a Google search for "Salvia divinorum" and consult the ads Google displays in the right margin.
Smoked Salvia can be a brute of a drug depending on the dose, as this FAQ on the Erowid drug site explains. (The drug can also be consumed orally.) "Generally, smoked salvia effects come on quickly, peak for 5-20 minutes, and then begin to subside," the FAQ notes. Users report visions; feelings of fright; loss of physical coordination; uncontrollable laughter; confusion; feelings of being underground, or underwater, or flying, or floating; experiences of "non-Euclidean" spaces...
Sgt. Gordy Disch of the Dane County Sheriff's Department tells the Wisconsin State Journal he worries about folks driving while tripping on Salvia, but he's obviously not viewed the YouTube videos. Salvia users tend to recline or go catatonic immediately after inhaling... I think Sgt. Disch should worry more about Ambien users and less about Salvia smokers."
(Text from Slate.com, image from Wikipedia)