Nootropic drugs are an area of great transhumanist interest, although still controversial. The main question is whether there exists drugs which enhance cognition beyond the normal level in healthy people, preferably with little side-effects. Other drugs might act by influencing chemical balances or by actually stimulating the brain in various ways. At present there does exist some positive results with cognition enhancing drugs in healthy animal and human subjects, but how useful the drugs really are remains uncertain. The most well understood paradigm is the cholinergic systems, which seem to be involved in memory encoding and attention.
Most drugs are much less powerful than the marketing hype.
A short introduction so smart drugs by Samu Mielonen. A good sceptical introduction. The New Edge A chapter about nootropics from Cyborg 101 . Keys to the Doors of Perception . About brain chemicals.