Below are some helpful links.
SAMHSA.GOV (Substance Abuse & Mental Health Services Administration)
SAMHSA store (many free publications)
Drugs: Shatter the Myths (free pdf)
Marijuana: Facts Parents Need to Know (free pdf)
DOT Office Drug & Alcohol Policy Overview (49 CFR part 40)
DOT Agency Information (website links to DOT agencies & lists their random rates)
Drug-Free Workplace Advisor (Dept of Labor program will customize a comprehensive drug screen employment policy)