Personally, I found Ayahuasca useful, in the "I'm going to drag you to a higher stage, screaming and kicking all the way" sense of useful. I wouldn't recommend it, but found it valuable. I don't know of anything except (specific) meditation to really get the necessary precision to make it to the higher stages.

As Hunter S. Thompson said, "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me.”.