Answer:
What is used by man, tossed by trees, everywhere but unseen?
There is one in every corner and two in every room.
What can get you there in eco style, pushed by your legs mile after mile?
I can be found in seconds, minutes and centuries, but not in days, years or decades.
What has feet on the inside but not on the outside?
Though not a plant, has leaves. Though not a beast, has spine. Though many wouldn't need this thing, It's more valuable than wine.