While these are valid solutions, exercise may be equally or even more effective.
John J. Ratey, one of the pioneers of ADHD [1], recently wrote the excellent Spark: The Revolutionary New Science of Exercise and the Brain[2]. In it, he explains in colorful details what happens in the brain, and why exercise may be the best treatment for a bunch of neurochemical imbalances - including ADHD.
[1] http://en.wikipedia.org/wiki/Driven_to_Distraction_(ADHD)
[2] http://www.amazon.com/Spark-exercise-improve-performance-bra...