This Site has a very comprehensive data base on drugs, their description, and effects.
National Institute on Drug Abuse
N.I.D.A. is a very informative Site, with links to numerous drug resource Sites.
Office of National Drug Control Policy
O.N.D.C.P. features many publications on drug abuse, treatment, and enforcement.
Drug Enforcement Administration
D.E.A. has drug data, wanted fugitives, programs, publications, and more on their Site.