This response might not entirely answer the question, but seeing as there have been some very good responses, I think it is important to make sure this does get mentioned.
I have struggled with AD/HD my whole life, but was only diagnosed maybe a couple years ago. Access to medication has been a blessing and a curse. I would like to point out (as mentioned above in the Wikipedia article) these medications have a very far reaching and serious list of side effects, and should only be used by people that genuinely need them, under supervision of a trained medical doctor. There is potential for abuse, and dosage is not something that is easy to figure out. It is very easy for people to over-medicate and become dependent.
I personally generally have to go to at least two different pharmacies (if not eight) once a month to pick up my medication, and this is a huge hassle. My point is that stimulant (and other AD/HD) medication is hugely abused, and very powerful, so it should not be treated like candy, it is prescription for a reason.
I don't want to be a buzzkill, I was kind of surprised that this topic would be openly discussed on the internet (not entirely sure why) and just wanted to make sure that it wasn't a "how to abuse AD/HD medication" thread. Nootropics as a whole I was unaware of, and I will definitely be checking out the links above to learn more.
To try and contribute to the conversation, I've heard that cognitive behavioral therapy (CBT) is something that might also be helpful in this regard. The wikipedia article doesn't seem very supportive of this, but I've heard very good things about it.