I've tried Modafinil (Provigil). My experience mirrors that of several close friends: It seems to do something different the first 1-2 times you take it as opposed to the rest.
That was 3-5 tries, spaced a week or two apart, several years ago.
These days, I stick to 5-HTP (the last precursor to serotonin (5-HT) that will cross the blood-brain-barrier (serotonin itself won't)) and B vitamins... and, of course, caffeine.
I've some friends who've recently said that Noopept[1] is pretty amazing. I've tried Piracetam[2] (though none of the other racetams) in the past and didn't notice any major effect.
To answer your headline question: I'm always on the lookout for stuff that will make me more efficient or effective, be it tools or molecules.
[1] http://en.wikipedia.org/wiki/Noopept
[2] http://en.wikipedia.org/wiki/Piracetam