Medscape, a web resource for physicians and other health professionals, has produced an interesting review of the medical uses for psychedelics.

Psychidelic Medicine: worth the trip? (Slideshow - free registration)
Psychedelic compounds have been used medicinally for millennia. Ancient Chinese, African, and South American healers prescribed them for various primarily psychiatric ailments, as did early Ayurvedic practitioners in India and possibly far older prehistoric cultures. One recent study[1] cites the possible influence of psychedelics on 40,000-year-old Paleolithic cave art. Despite extensive early 20th century interest in hallucinogens as therapy, modern medicine mostly abandoned research into their therapeutic potential, as governments worldwide criminalized agents such as LSD, psilocybin, and mescaline in reaction to their counterculture use in the 1960s. But scattered clinical curiosity over the years and a recent renewed interest in psychedelic treatments have hallucinogens again emerging as possible psychiatric therapies, or at least as pharmacologic leads on related and potentially helpful compounds. Medscape