Neuro-linguistic Programming et. al. It's currently considered a pseudo-science (which is technically false: it's
pre-scientific. However, unfortunately, many practitioners and promoters do try to make it seem more scientific than it is.)
It's actually fairly widespread, people teach it and use it all over the globe, and fairly stodgy organizations have used it (e.g. the US Army.) Yet the mainstream rarely mentions it, and then only to denigrate it. However, this seems to me to be that stage right before something goes from "fringe" to "common knowledge".
Once NLP goes fully mainstream there will be a sea change in human society. Psychological hangups will be a thing of the past. There will still be people who have mental problems, but they will be the ones with actual physical problems with the brain (or whatever) as opposed to just bad programming. Things like addictions, phobias, neurosis, etc. will vanish.
Educational possibilities are mind-blowing. Learning multiple languages becomes easy, as does learning musical instruments and dances. Really any behavioral patterns will become subject to symbolic manipulation. Competitive sports will be transformed when each player can "clone" the best moves of the best players.
Politics has already been revolutionized by NLP innovations. As far back as G.W. Bush NLP language patterns had already made their way into political speeches. The current culture wars are, at their root, gangs of hypnotists programming furiously.
To me the fascinating thing is that, once it's common knowledge that you can alter your psychology as easily (more easily!) than your wardrobe it becomes a matter of personal responsibility. The whole "it's just human nature" argument goes out the window when you can reprogram yourself.