There are some over the counter remedies out there, but I think most people here would agree that the best medication for situational anxiety would be a benzodiazepine. This class of drugs includes Xanax, Valium, Ativan, and many others. Doctors often prescribe these drugs for exactly what you're looking for, that is to take before a dreaded event such as presentation or meeting. If you're looking for non-prescription drugs I would start with kava kava.
Peace
Have you tried Kava Kava, if so how did you get it ? I heard it was banned in north america.