The pop article "Can LSD cure depression?" covers some of the recent and upcoming research using psychedelics. Ecstasy (MDMA), for example, appears to be successful in helping people make significant progress with PTSD in just one or two sessions. Psilocybin may help people overcome nicotine dependency.
Psilocybin has been shown to reduce blood flow in certain areas of the brain. Feilding says "it may also be significant that the volunteers
who reported the most vivid and powerful experiences were also those who had
the greatest reduction in blood flow." Meditation has shown similar changes in blood flow, and as a sample of one, I'd say psilocybin seems to "reach" me much more easily after a few years of daily meditation.