Erowid is the original (1995), and still highly regarded, website that documents drugs and their uses. It provides non-judgmental information. Although great in value, the site can sometimes be difficult to navigate.
“Documenting the Complex Relationship Between Humans & Psychoactives”
“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. We also strive to ensure that these resources are maintained and preserved as a historical record for the future.”
You can find information about Psychoactive Plants and Drugs here.
There is also a library of books here.