The 5-5 point seems to be the most popular opening.
There are many choices after 3-4, but of these, h-k have appeared only once in the set.
bugcat: For what it's worth, a dan player once told me that they had never lost on 9x9 against an opponent who opened with 3-4.
Choice a appears about twice as often as any other choice.
Choice a is about twice as popular as anything else, and f appears only once.
Choice a is more popular than the others.