Quand tu veux construire un bateau, ne commence pas par rassembler du bois, couper des planches et distribuer du travail, mais reveille au sein des hommes le desir de la mer grande et large.
And here is the translation proposed instead of the one that circulates on the Internet:
When you want to build a ship, do not begin by gathering wood, cutting boards, and distributing work, but awaken within the heart of man the desire for the vast and endless sea.
Because I am using the cat, for the English version I switched "of man" to "your" which fits with the second-person style that starts the adage; I left the French the same as cited. I found the image at Cheezburger but because there are too many words for a LOLCat, I used Automotivator to make the poster: