A few years ago I started smoking a lot of pot and spent most of my time high. I was also into spiritual growth and personal development. In fact, I read the Power of Now, seen What The Bleep Do We Know, watched a PBS special on string theory, read countless articles and self help books, and practised meditation; all when I was stoned. I have experienced profound truths and inderstandings of the universe and how it works along with learning to identify my awareness thanks to the aid of mary jane.
Sometimes when I feel like my life has gotten a little off track, I will smoke a little bit, do some deep breathing exercises, and let my awareness recognize thoughts and thought patterns (which automatically disconnect the awareness from the dreams of those thought patterns which in turn calms the mind) and then simply let answers to my questions simply come to me. The next day I will feel fresh and find myself back on course.
I read the Taoist book, Multi-Orgasmic Man, and found that I was able to learn how to circulate my sexual energy when I was high which enhances sexual pleasure. This is a lesson I have taken with me.
In all of my experiences I have learned that anyone one thing is not intrinsically good or bad, what makes something good or bad is what we do with it. If people can use marijuana as a tool for personal growth, more power to them. I personally find that when using marijuana, one or two hits serves my intentions well (the ancient yogis would recommend only on the full moon).
And as an fyi, there are different strains of marijuana, The sativa strain is mildly psychoactive.
Here are some links to some related resources on the net
An article about marijuana and sex Psychedelic Yoga - Mediation techniques while on psychedelic drugs which include marijuana Jesus Used Marijuana including the history of marijuana and human consciousness