If you are interested in a wonderful repository of great quotations, I highly recommend brainyquote.com.

In the meantime, here are some of my favorite quotations:

 

"I disapprove of what you say, but I will defend to the death your right to say it."
         -attributed to Voltaire

"I'll make him an offer he can't refuse."
         -Mario Puzo, "The Godfather"

"The worth of a state, in the long run, is the worth of the individuals comprising it."
         -John Stuart Mill

"A teacher affects eternity. He can never tell where his influence stops."
         -Henry Brooks Adams

"The art of teaching is the art of assisting discovery."
         -Mark Van Doren

"Nobody goes there any more, because it's too crowded."
         -attributed to Yogi Berra

"You can take time off, but you can never put it back."
         -found on a Salada Tea Bag "Tag Line"

"We must not confuse dissent with disloyalty."
         -Edward R. Murrow

"Don't look back. Something may be gaining on you."
         -Satchel Paige

"A free press can of course be good or bad, but, most certainly, without freedom it will never be anything but bad."
         -Albert Camus

"I'm mad as hell, and I'm not going to take it anymore."
         -Paddy Chayevsky (from "Network" screenplay)

"The real problem is not whether machines think but whether men do."
         -B.F. Skinner

"Never tell people how to do things. Tell them what to do and they will surprise you with their ingenuity."
         -Gen. George S. Patton

"We admit of no government by divine right. The only legitimate right to govern is an express grant of power from the governed."
         -William Henry Harrison

"Minds are like parachutes. They only function when they are open."
         -Sir James Dewar

"The satisfaction of solving a problem is the difference between work and drudgery."
         -Dale Dougherty

"We make a living by what we get, but we make a life by what we give."
         -Winston Churchill

"If we were to wake up some morning and find that everyone was the same race, creed, and color, we would find some other causes for prejudice by noon."
         -George Aiken