I have tried one recently that is available from health food and supplement vendors online and off. It is called piracetam. There have been some studies done on this one, which show some real effects. As for my experience, I can say that I am convinced it helps me concentrate. In fact, instead of the thirty blog posts that I might normally write in a day when I want to promote my websites, I wrote over one hundred the first time I tried piracetam. 12,000 words, and they came easily. I was focused on the task to say the least.