Modafinil improves the mental functioning of healthly volunteers:

Danielle Turner, from the Department of Psychiatry at the University of Cambridge, says modafinil could revolutionise current understanding of the way we form and retain memories. It seems to have a unique mechanism of action in the brain.

"In the study, the volunteers given modafinil performed significantly better at neuropsychological tests involving short-term memory and showed less impulsive responding and an increased tendency to reflect on the tasks they were given," she said.

Modafinil provided this benefit without the side effects seen with amphetamines and other drugs:

Sixty healthy young men were tested using touch-sensitive computer screens and easy-to-understand computer games after they were given either a dummy tablet or modafinil.

The ones on modafinil showed improved ability in planning complex problems, recalling longer strings of numbers and remembering abstract patterns.

Modafinil is available as Provigil and is used to treat narcolepsy (uncontrollable sleepiness). Read more about modafinil here and here and also here as Provigil. You can also read an ABC News article on modafinil as well this article which includes mention of military uses for modafinil.