The first that comes to mind is modafinil (you can look it up here: http://overclockingthebrain.com/modafinil/) because it is designed for promoting wakefulness. But modafinil is difficult to get without prescription in many countries.
Other non-caffeinated nootropics are not really wakefulness promoting as far as i know, but some can significantly improve the effect of caffeine (hence you need less of it). Some caffeine shots are based on this - you can give them a try.