Answer:
I am the only thing that place today before yesterday. (one word)
I fill a room but take no space. What am I?
I am the tool for inspiring many. Buy me in the store for not much more than a penny. Don't overuse me, or my usefulness will go. What am I?
I'm not really more than holes tied to more holes; I'm strong as good steel, though not as stiff as a pole.
I am taken from a mine and shut in a wooden case from which I am never released. Yet I am used by almost everybody. What am I?
I am the kind of an ant that's good at math. What am I?