"Documenting the complex relationship between humans and psychoactives"
Thats the tag line for Erowid, the most extensive web site (I know of) about psychoactive substances. The site is a rich storehouse of information... scientific, experiential, and legal. For accurate information about drugs and their effects, including shamanistic uses, check out this website. Erowid presents clear minded information, without the "thought crime" hysteria found on most sources re: this topic.
Read Erowid and just say "yes".