New Advent, Catholic Online, and EWTN provide great articles about the very first Franciscan.
And two of his most famous prayers:
O Lord, make me an instrument of Thy Peace!
Where there is hatred, let me sow love;
Where there is injury, pardon;
Where there is discord, harmony;
Where there is doubt, faith;
Where there is despair, hope;
Where there is darkness, light, and
Where there is sorrow, joy.
Oh Divine Master, grant that I may not
so much seek to be consoled as to console;
to be understood as to understand; to be loved
as to love; for it is in giving that we receive;
It is in pardoning that we are pardoned;
and it is in dying that we are born to Eternal Life.
Most high, all powerful, all good Lord! All praise is yours, all glory, all honor, and all blessing. To you, alone, Most High, do they belong. No mortal lips are worthy to pronounce your name.
Be praised, my Lord, through all your creatures, especially through my lord Brother Sun, who brings the day; and you give light through him. And he is beautiful and radiant in all his splendor! Of you, Most High, he bears the likeness.
Be praised, my Lord, through Sister Moon and the stars; in the heavens you have made them, precious and beautiful.
Be praised, my Lord, through Brothers Wind and Air, and clouds and storms, and all the weather, through which you give your creatures sustenance.
Be praised, My Lord, through Sister Water; she is very useful, and humble, and precious, and pure.
Be praised, my Lord, through Brother Fire, through whom you brighten the night. He is beautiful and cheerful, and powerful and strong.
Be praised, my Lord, through our sister Mother Earth, who feeds us and rules us, and produces various fruits with colored flowers and herbs.
Be praised, my Lord, through those who forgive for love of you; through those who endure sickness and trial. Happy those who endure in peace, for by you, Most High, they will be crowned.
Be praised, my Lord, through our Sister Bodily Death, from whose embrace no living person can escape.
Woe to those who die in mortal sin! Happy those she finds doing your most holy will. The second death can do no harm to them.
Praise and bless my Lord, and give thanks, and serve him with great humility.
(UPDATE: 10/4/2013): Here is an article stating the first prayer may not be attributed to him.
Originally posted 10/4/2006.