Cannabis

Smoking Marijuana: Basic Facts - Summary information about many aspects of marijuana usage.
http://www.geocities.com/healthmoon/smoking-marijuana/

Cannabis - Information on marijuana, how it is taken, and effects it has on the body.
http://www.drugs-info.co.uk/drugpages/cannabis/cannabis.html

For Potheads, Brain Remains Impaired Long After the Buzz Is Gone - Article on the effects of marijuana use, based on a study by researchers at Harvard University, and reported in 1996 in the Journal of the American Medical Association.
http://www.mentalhealth.com/mag1/p5m-sb01.html

Cognitive Deficits in Marijuana Smokers Persist After Use Stops - Report in 2003 about a study showing that cognitive impairments resulting from smoking marijuana can last up to at least 28 days after an individual last smoked the drug. The study was supported by the National Institute on Drug Abuse.
http://www.drugabuse.gov/NIDA_Notes/NNVol18N5/Cognitive.html

A Collection of Articles That Address Research on Marijuana - Publications of the National Institute on Drug Abuse, extending back as far as 1995.
http://www.drugabuse.gov/NIDA_Notes/NN0058.html

Cognitive Deficits Associated With Heavy Marijuana Use Appear To Be Reversible - Report in 2002 about a study showing that memory and learning problems caused by heavy marijuana smoking persist for at least a week after cessation of use of the drug, but they appear to resolve completely within a month. The study was supported by the National Institute on Drug Abuse.
http://www.drugabuse.gov/NIDA_Notes/NNVol17N1/Cognitive.html