National Institute on Drug Abuse of the National Institutes of Health:
NIDA - This site offers the latest scientific research related to drug abuse from the NIH. View mechanisms of drug action in the brain. Download free guidelines and manuals based on the most current scientific finding (start with Preventing Drug Use Among Children and Adolescents, A Research Based Guide). You can even view national drug abuse research conferences live on the Internet.
Substance Abuse and Mental Health Services Administration
SAMHSA - This is the Big Top Tent for a multitude of Federal services related to alcohol, drug abuse, and mental health including: SAMHSA - The National Clearinghouse for Alcohol and Drug Abuse Information