Prayers of the Saints
Click on the picture of each saint to get to Catholic Online's page for that saint.
A Prayer by Thomas Aquinas
Grant me, oh Lord my God,
a mind to know you,
a heart to seek you,
wisdom to find you,
conduct pleasing to you,
faithful perseverance in waiting for you
and a hope of finally embracing you.
--  St. Thomas Aquinas
Aquinas's Student Prayer
Creator of all things,
true source of Light and Wisdom,
lofty source of all Being,
graciously let a ray of Your Brilliance penetrate into the darkness of my understanding and take from me the double darkness in which I have been born,
sin and ignorance.
Give me a sharp sense of understanding, a retentive memory, and the ability to grasp things correctly and fundamentally. 
Grant me the talent of being exact in my explanations, and the ability to express myself with thoroughness and charm.
Point out the beginning, direct the progress, help in the completion.
Through Christ, our Lord.
St Patrick's Prayer
Christ, as a light, illumine and guide me!
Christ, as a shield, o'ershadow and cover me!
Christ, be under me!
Christ, be over me!
Christ, be beside me, on left hand and right!
Christ, this day be within and without me!
Christ, the lowly and meek,
Christ, the all powerful,
be in the heart of each to whom I speak, in the mouth of each who speaks to me,
in all who draw near to me, or see me, or hear me!
-- this is a piece of the Lorica, a much longer prayer
A Prayer of St. Theresa of Lisieux
Oh my God, I ask of you for myself and for those whom I hold dear, the grace to fulfill perfectly your holy will,
to accept for love of you the joys and sorrows of this passing life, so that we may one day be united in Heaven for all eternity.
Augustine's Prayer to the Holy Spirit
Breathe in me, Holy Spirit, that my thoughts may all be holy.
Act in me, Holy  Spirit, that my work too may be holy.
Draw my heart, Holy Spirit, that I may love only what is holy.
Strengthen me Holy Spirit, to defend all that is holy.
Guard me, Holy Spirit, that I may always be holy.
A Prayer of Saint Anthony of Padua
Behold the Cross of the Lord!
Begone, ye enemy powers!
The Lion of the Tribe of Judah, the root of David, has conquered! Alleluia!
A Prayer of St Teresa of Avila
Let nothing disturb thee,
nothing afright thee
all things are passing,
God never changes!
Patient endurance
attaineth to all things
who God possesth
in nothing is wanting
alone God sufficeth.
A Prayer of  Nikolaus von der Flue
My Lord and my God,
take from me everything
that keeps me from reaching you.
My Lord and my God,
give me everything
that will bring me close to you.
My Lord and my God,
take me away from myself
and give me to you.
These are just a few prayers of the saints that I particularly like.  Feel free to email me with your own favorites!