There are at least two major universities now doing clinical trials for the hallucinogen psilocybin. NYU has a trial going with cancer patients.
http://www.nyucanceranxiety.org/index.html
And Roland Griffiths at Johns Hopkins has several trials going. I signed up for one of them, but I didn't meet their criteria. Just search his name and you'll find all kinds of stuff. He's done TED talks, and they're all over YouTube.
http://neuroscience.jhu.edu/research/faculty/33
Both groups are careful to emphasize that the context in which you take these drugs is very important. They work to keep things as calm as possible, so that there are no "bad trips," by having not one but two trained guides in the room at all times.