Went hiking yesterday and saw this small sassafras tree on the Mohonk Preserve (they're pretty common).
Sassafras (Sassafras albidum) is easily recognized by its leaves - some are oval, some mitten shaped, and some have three lobes. Here's a typical leaf:
Sassafras has long been used in traditional medicine was even a flavoring added to root beer before its use was banned (see below). The roots can be diced and steeped to make tea which was used as a general tonic and was said to have diaphoretic and diuretic properties. One traditional name for the sassafras tree was "ague tree" ("ague" refers to a fever with chills and sweating).
The wood of sassafras was commonly used in the past for cabinets since the scent was thought to keep insect pests away. The pleasant aroma of the tree was said to give healing and protection from evil influences in folk medicine.
A problem with sassafras is that it contains a chemical called safrole. Safrole (C10H10O2 or 5-(2-propenyl)-1,3-benzodioxole) is considered by the Food and Drug Administration to be a weak carcinogen and hepatotoxin (damages the liver) and its use has been banned in foodstuffs. This is based on studies in rats which were fed very large amounts of pure safrole. Occasional use of sassafras tea is probably not going to cause you any harm (or at least no more so than much of what else we ingest on a daily basis - you'd be surpised by what "natural" foods we eat can cause cancer in large amounts). Pregnant women should avoid it, however, since it does have abortifacient effects.
Anyway, here's a website listing things sassafras has medicinally been used for (and lots of dire warnings).
Interestingly, safrole is a one of the chemicals used in synthesizing MDMA (ecstasy) and is now a controlled substance (note - sassafras tea does not make you high!).