How about gingko biloba?
(Oldest tree on earth, but supposedly the stuff sold in pill form is not the same part of the plant used by the Chinese use for medicinal purposes)
Don't use if you have thin blood or are on blood-thinning medications. Gingko reportedly increases blood flow between the brain hemispheres.
I have found, however, that gingko does pretty much zip for short-term use. Not piracetam. Check this shit out, it's great fun (not too expensive, and [quasi-] legal).
Don't take the recommended dosage. I find it makes you too smart. (no joke, beware, you'll find yourself pissing off your friends/colleagues a lot more than usual)
note: take in combination w/ a choline supplement like DMAE (available at your local General Nutrition Center [2 for $13.99, and all you need is 1 per day, forget the "1-4 a day" instructions] or Lucidril, very good stuff)
Oh yea, piracetam is not an herb. It was developed in the 1960's as a "nootropic", a "class" of drugs scientists hoped would promote brain clarity and protect the brain from various toxic agents [piracetam has been found to protect against alcohol poisoning, curare-like agents, and barbituates] with minimal to no side effects.
Since piracetam slightly lowers acetylcholine levels, expect minor headaches if you don't take it in combination with a choline supplement.
(P.S. the price ranges are wide when ordering from an internet supplier, so do a little searching; it'll all turn out right in the end, you'll see!)