Shrooms are one thing I'd like to try myself as well. There've been studies done, and psilocybin gives you about an extra half a standard deviation of "Openness to Experience", which is the psychological dimension corresponding roughly to things like creativity, curiosity, and receptiveness to emotional experiences. Based just on that, they're the only drug I'm aware of that might legitimately be called "mind-expanding". Hard to get in the states, yeah.