On the strength of the psilocybin research, it wouldn't surprise me to learn LSD increased Openness as well.

Might find my http://www.gwern.net/LSD%20microdosing interesting.

My experiences with speed reading are that once you get up to a certain speed, your thinking speed is the limiting factor, not the way your eyes move. Correct me if I'm wrong, but most speed reading techniques offer nothing in terms of how to think quicker. Rather, they are methods of moving your eyes more efficiently.

Extreme immersion into some narrow skill or mode of thought. For instance, doing nothing other than playing chess or tetris or minecraft during all waking time for a month. This seems like it would have big cognitive effects. I'm not sure whether the effects would be good or bad, but it's certainly worth trying.

In my experience, doing stuff like that screws up my cognition in far less than a month -- even after two days of doing the same thing “during all waking time” I start to feel I'm (temporarily) losing my ability to think in a normal way. YMMV.

There's evidence that juggling and playing tetris increase white matter.

For some reason I found learning to shoot a hockey puck with either hand as the dominant one much easier than trying to do the same for either hitting or throwing a baseball. Throwing a football left handed is even more difficult than the baseball motor skills. Catching a baseball with the right hand was easiest of all to learn (as I learned to catch with my non-dominant hand, as Americans tend to be trained).

There may be a universal hierarchy of the difficulty of these skills, with some easier to start with.

From Exploring the World of Lucid Dreaming:

I discovered in high school that I was a lucid dreamer when I learned that I could study complicated mathe-matical and geometry problems before going to bed and discovered that I was able to solve the problems when I awakened. This phenomenon followed me through college and medical school. When I was in medical school, I began to apply my sleep-solving abilities to medical problems, quickly running through the questions of the day and usu-ally finding useful solutions or useful additional ques-tions in the process (even today I will occasionally wake up at 3: 00 in the morning and call the hospital to order a special laboratory test on a problem patient, the pos-sible solution of which had occurred to me in a lucid dream). At this point, the greatest use to which I have been able to put this facility is in the practice of surgery. Each night before retiring I review my list of surgical cases and I actually practice these cases in my sleep. I have gained a reputation for being a rapid and skilled surgeeon with almost no major complications. This surgical “practice” has allowed me from the very beginning to constantly review the anatomy and to refine and polish technique by eliminating unnecessary motions. I am presently able to perform most major complex procedures < 35 percent to 40 percent of the time taken by most off my peers. (R. V., Aiken, South Carolina)

I recently pulled second place in a math competition. When I received a copy of the problems (five in all), I spent most of the day mulling over various approaches. When I went to sleep that night, I dreamed lucidly of looking through a particular math reference book I own. I don’t think I dreamed of reading anything in particular in the book, just the act of flipping through it. Subjec-tively, the dream was only a couple of seconds long. When I woke, I didn’t have an opportunity to look through the book until that evening. When 1 did, 1 discovered the trick I needed to solve one of the problems. (T. D., Clarksville, Tennessee)

A little over a year ago, I was in a linear algebra class that introduced me to vector spaces. I was having a lot of trouble understanding the topic on more than a superficial level. After about a week of serious studying, I had a lucid dream about an abstract vector space. I perceived directly a four-dimensional space. The dream did not have a visual component, but such abstract dreams are not uncommon for me. The best I can describe that dream is to say that I perceived four coordinate axes that were mutually perpendicular. Since that night, both math and dreaming have been more fun for me, and I’ve had relatively little trouble understanding vector space calculus. (T. D., Clarksville, Tennessee)

There's a lot of mostly-unexplored territory in lucid dreaming. For instance, people have reported growing more eyes and seeing through all eyes simultaneously, or even being able to see in all directions at once. I once opened a poetry book in a lucid dream and found a poem I hadn't ever seen before, and on waking the poem actually seemed pretty good.

Piotr Woźniak doesn't seem to think lucid dreaming is worth pursuing.

Though speaking from my personal experience, it's pretty fun, and for that you don't have to be good at it; my control was pretty limited (flying is easy).

My personal experience is my visual imagination is far more vivid but my verbal reasoning is much diminished. I've semi-consciously thought through and planned social situations, and I hazard that it might be useful in artistic fields or in design, where what is important is to 'experiment' with lots of possible visual designs then pick a single one, which diminishes the problems caused by not taking notes as you only have to remember the final result. (Plausibly the reports of people waking up with fully formed paintings/music are semi-subconscious instances of this.)

TMS?

Probably transcranial magnetic stimulation.

writing things on lesswrong, so one's ideas are given non-insane feedback