I've used Huperzine-A I believe its called? It helped with my studying a bit, although it toned down my emotions also, so there was a trade-off.
I also recently used Phenibut, which was pleasant, took my anxiety down quite a notch, and I blew through all 100 grams in around a month. The first few days it felt very amazing, next to no anxiety, all smiles and laughs, felt very social, almost drunk but with a clear head, although I had problems concentrating. Tolerance built up very fast, and i found on my days off i was a bit more anti-social and had more anxiety. Its very tempting to keep on using more and more though. So i've decided I'm not going to re-order, as i've got a history of addiction, and as a result withdrawal.
From what i've read, and don't take my word, but green tea has l-theanine and caffeine, hence the calmer more focused effect it has in comparison to black coffee. I have not tried the l-theanine substances though.
I would love to try piracetam with choline for this upcoming semester, but I doubt I will due to money constraints.
I'm sure you've gone to erowid's smart drug vaults, but if not here is a link . http://www.erowid.org/smarts/smarts.shtml