Erowid is a member-supported organization providing access to reliable, non-judgmental information about psychoactive plants, chemicals, and related issues. We work with academic, medical, and experiential experts to develop and publish new resources, as well as to improve and increase access to already existing resources. They also strive to ensure that these resources are maintained and preserved as a historical record for the future.
Erowid provides the largest amount of personal accounts of drug uses on the internet and could be considered the bases of underground research of illegal drug use today. I believe this is one of the greatest resources of drug use research since it is not possible for universities to conduct ethical research into the use of psychoactive drugs.
Check out their website to read endless amounts of information on the drug community and how psychoactive plants may help further the studies into the human mind.