SAMHSA's Center for Substance Abuse Prevention:

Information about model programs, training and technical assistance, other organizations working to prevent substance abuse, and much, much more!
http://www.samhsa.gov/centers/csap/csap.html

Centers for Disease Control and Prevention:

Lots of information on a variety of health-related topics, including many statistics.
http://www.cdc.gov/

FedStats:

The one-stop site for statistics from federal agencies. Be sure to check out the topical links (includes links to stats on teen cigarette brand preferences, AIDS/HIV, income, etc.) and the MapStats for Wisconsin information.
http://www.fedstats.gov

National Clearinghouse for Alcohol and Drug Information (NCADI)/ PREVLINE:

NCADI provides a variety of resources on alcohol and other drugs, as well as providing access to several databases of research information.
http://www.health.org

National Institute on Alcohol Abuse and Alcoholism (NIAAA):

The information on clinical trials and the research databases available through the NIAAA site make it a good resource for anyone interested in alcohol-related topics.
http://www.niaaa.nih.gov/

National Institute on Drug Abuse (NIDA):

The NIDA site has sections for students & young adults, parents & teachers, and researchers & health professionals, with information on drugs targeted to each audience. From research findings to curricula and slide presentations, there's something here for everyone!
http://www.drugabuse.gov/

National Institutes of Health:

As well as including NIAAA and NIDA, the national Institutes of Health is a rich resource for information on any health-related topic-from scientific research to funding opportunities to quick facts.
http://www.nih.gov

Partners for Substance Abuse Prevention (PSAP):

Sponsored by CSAP/SAMHSA, the PSAP website was developed as a virtual meeting place for organizations involved in substance abuse prevention and related activities. PSAP will provide organizations networking opportunities, information, and resources to aid in continuing their work as well as helping those new in the field to get active in substance abuse prevention. Partners include: national organizations, foundations, workplaces and businesses, community coalitions, grass roots organizations, faith based groups, universities and educational institutions, federal, state and local government entities, criminal justice organizations, health institutions, and professional associations.
http://www.samhsa.gov/preventionpartners/

Prevention Pathways:

Sponsored by the Substance Abuse and Mental Health Services Administration's Center for Substance Abuse Prevention (CSAP). Prevention Pathways is a "gateway to information on prevention programs, program implementation, evaluation technical assistance, online courses, and a wealth of other prevention resources."
http://www.samhsa.gov/preventionpathways/