My personal favorite:
"If you tremble with indignation at every injustice then you are a comrade of mine." -- Ernesto "CHE" Guevara
Some other good ones:
"Strive every day so that (our) love of living humanity will be transformed into actual deeds, into acts that serve as examples, as a moving force." -Ernesto "CHE" Guevara
"Let me say, with the risk of appearing ridiculous, that the true revolutionary is guided by strong feelings of love. It is impossible to think of an authentic revolutionary without this quality... One must have a large dose of humanity, a large dose of a sense of justice and truth, to avoid falling into extremes, into cold intellectualism, into isolation from the masses. Every day we must struggle so that this love of living humanity is transformed into concrete facts, into acts that will serve as an example." -Ernesto "CHE" Guevara
"Capitalism is the extraordinary belief that the nastiest of men, for the nastiest of reasons, will somehow work for the benefit of us all." -- John Maynard Keynes
"I see in the near future a crisis approaching that unnerves me and causes me to tremble for the safety of my country. ... corporations have been enthroned and an era of corruption in high places will follow, and the money power of the country will endeavor to prolong its reign by working upon the prejudices of the people until all wealth is aggregated in a few hands and the Republic is destroyed." -- President Abraham Lincoln, 1864
"Virtue tends always to go barefoot on stones and thorns while those who represent infamy and degradation recline on soft cushions in golden carriages. " - Jose Isabel Herrera
"Peace cannot be understood merely as military demobilization; Rather it should be seen as a process of creating social justice." - Manual Pérez Martinez Commander-in-Chief ELN Colombia
"You cannot send your young people to hunt for terrorists in caves in Central Asia and at the same time have terrorists with whom you drink with a bar in Miami every night." -- Ricardo Alarcon
"By having no family,
I inherited the family of humanity.
By having no possessions,
I have possessed all.
By rejecting the love of one,
I receive the love of all.
By surrendering my life to the revolution,
I found eternal life.
Revolutionary Suicide."
-Huey P. Newton
"He who opens a school door, closes a prison."
-- Victor Hugo
"God either wishes to take away evil, and is unable, or He is able, and unwilling; or He is neither willing nor able, or He is both willing and able. If He is willing and is unable, He is feeble, which is not in accordance with the character of God; if He is able and unwilling, He is envious [malicious], which is equally at variance with God; if He is neither willing nor able, He is both envious and feeble, and therefore not God; if He is both willing and able, which alone is suitable to God, from what source then are evils? or why does He not remove them?" -- Epicurus
"Fear of power invisible, feigned by the mind, or imagined from tales publicly allowed, RELIGION; not allowed, SUPERSTITION." -- Thomas Hobbes