My current favorite is this from George Bernard Shaw (I believe):
“Youth is wasted on the young”
Here’s one that I have always like from the film, “Restoration”.
Misfortune may leave behind
unlooked for blessings.
The stars that once confused me
seem now to light a path that is clear,
that, I have, in truth been traveling
for all these years.
Where I met what came
and left behind my sorrows,
and I am traveling still.
Robert Merivel
“When a stupid man is doing something he is ashamed of, he always declares that it is his duty.” – G.B. Shaw, Caesar and Cleopatra.
“Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin to slit throats.” – H.L. Mencken
“But that was in another country, and besides the wench is dead.” Christopher Marlowe. (I don’t remember a damn thing about the play, but that line stuck.)
“The test of an adventure is that when you’re in the middle of it, you say to yourself, ‘Oh, now I’ve got myself into an awful mess; I wish I were sitting quietly at home.’ And the sign that something’s wrong with you is when you sit quietly at home wishing you were out having lots of adventure.” – Thornton Wilder, The Matchmaker
“Don’t waste time with old cliches.” – Batman
“Quit fiddling around here and go read my bodhran joke in the whistle forum.” – gonzo
She was just a deathly cool lady, wasn’t she? 
One I have very much tried to live by is:
“Beauty and grace will be performed whether or not we will sense them, the least we can do is try to be there.”
-Annie Dillard, Pilgrim at Tinker Creek
In this life we cannot do great things. We can only do small things with great love. - Mother Teresa
Looking that one up brings another:
Do not wait for leaders; do it alone, person to person. - Mother Teresa
Another one about walking the walk, instead of talking the talk:
“Whatever you can do or dream you can, begin it. Boldness has genius, power and magic in it.” - Goethe
One site says this famous quote may not be from Goethe, and is a poorly translated version of:
Der Worte sind genug gewechselt,
lasst mich auch endlich Taten sehn!
Enough words have been exchanged;
now at last let me see some deeds! (Goethe, Faust I)
And finally, some of my personal favorites:
“Nothing we do is hard, we make it hard.”
“I don’t have to ‘fix’ all the problems in my life in the next five minutes, it took me X number of years to get where I am, it may take some time to get out. I can do it one step at a time.”
- yours truly
Here are some more good ones all from Einstein:
The most important decision we make is whether we believe we live in a friendly or hostile universe.
Out of clutter, find Simplicity. From discord, find Harmony. In the middle of difficulty lies opportunity.
We can´t solve problems by using the same kind of thinking we used when we created them.
Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius - and a lot of courage - to move in the opposite direction.
I am enough of an artist to draw freely upon my imagination. Imagination is more important than knowledge. Knowledge is limited. Imagination encircles the world.
Reality is merely an illusion, albeit a very persistent one.
The most important human endeavor is striving for morality in our actions. Our inner balance and even our very existence depends on it. Only morality in our actions can give beauty and dignity to our lives.
“Everybody wants to go to heaven, nobody wants to die”
-Anon
"Feelings that would not have disgraced a leader who, now that the snow has begun to fall and the mountain top is covered in mist, knows that he must lay himself down and die before morning comes, stole upon him, paling the colour of his eyes, giving him, even in the two minutes of his turn on the terrace, the bleached look of withered old age. Yet he would not die lying down; he would find some crag of rock, and there, his eyes fixed on the storm, trying to the end to pierce the darkness, he would die
standing. "
-Virginia Woolf, from To the Lighthouse
“People can’t handle prosperity.”
- My Dad
And altering CHC’s above, when I talk about Berkeley types who have figured out how to impose the perfect progressive society (based on a lot of taxation and regulation) on the rest of America, and those with the opinions are living under special financial arrangements, like parent’s money, trust funds, grants and nut money (SSI) but expecting full rights and privileges, I like to say:
“Everybody wants to come to the party, but nobody wants to buy the beer.”
“Here’s some advice for you: don’t do it.”
–Attributed to Irish flute player, orator and piper Kevin Henry regarding someone’s question about taking up pipering
“Between stimulus and response there is a space. In that space is our power to choose our response. In our response lies our growth and our freedom.” --Viktor E. Frankl , M.D., Ph.D.
Being un-original, and grandiloquent and boastful, I shall quote myself: 
Then reveal my source:
老子: 「道德经」: 第九章
持而盈之，不如其已﹔
揣而锐之，不可长保。
金玉满堂，莫之能守﹔
富贵而骄，自遗其咎。
功遂身退，天之道也。
Laozi: “Dao De Jing”: Ninth chapter
Fill a cup to its brim and it is easily spilled;
Temper a sword to its hardest and it is easily broken;
Amass the greatest treasure and it is easily stolen;
Claim credit and honor and you easily fall;
Retire once your purpose is achieved - this is natural.
老子: 「道德经」: 第七十一章
知不知，尚矣﹔不知知，病也。
圣人不病，以其病病。
夫唯病病，是以不病。
Laozi: “Dao De Jing”: 71st chapter
Who recognizes his limitations is healthy;
Who ignores his limitations is sick.
The sage recognizes this sickness as a limitation.
And so becomes immune.
“Maybe your folks never warned you about this, but you never, ever disturb a solitary post in a field. Because it may not just be a marker…it may be holding something down.”
“Guess just because you can do something doesn’t mean you should.”
“Everyone just acted like no one was responsible. Well, that won’t wash. If no one is responsible, then everyone is responsible.”
–quotes from “Night Calls”, by Katharine Eliska Kimbriel
That’s one of my favorites, too, I was even going to include it in my list. Here are some others.
“The road to truth is long, and lined the entire way with annoying bastards.”
- Alexander Jablokov -“The Place of No Shadows”
“I have the heart of a little boy. I keep it in a jar on my desk.” - Stephen King -
“Clothes make the man. Naked people have little or no influence on society.” - Mark Twain -
“It was a blonde, a blonde to make a bishop kick a hole in a stained glass window.” - Raymond Chandler -
“The only difference between me and a madman is that I’m not mad.” -Salvador Dali, painter (1904-1989)-
“After two years in Washington, I often long for the realism and sincerity of Hollywood.” -Fred Thompson, US senator, lawyer, writer, and actor (1942-present)-
“We rose to bring about Eutopia,
But all we got was Dev’s myopia”
Oliver St. John Gogarty.
“An Irishman’s heart is nothing but his imagination”
George Bernard Shaw.
“You can be in my dream if I can be in yours”
Bob Dylan.
Slan,
D.
…I gave her gifts of the mind. I gave her the secret sign
That’s known to the artist who has seen the true gods of sound and stone
And word and tint…
Thanks for reminding me, Dub. They are the true gods (all the ones I need anyhow!). I shall post a photo of me sitting next to Paddy before April’s out… 
Assuming that is the quote I posted up recently, it was from a quick google and I only noticed later that there was a terrible mistake in it. The original verse is " …who has known the true gods..". Known being a much more crucial word than seen, in the context.
He’s always there…
Slan,
D.
“What fairy tales give the child is his first clear idea of the possible defeat of bogey. The baby has known the dragon intimately ever since he had an imagination. What the fairy tale provides for him is a St. George to kill the dragon.” --G. K. Chesterton
And the woman inside my house
She won’t stop talking
She never says a thing
She just keeps talking
And I might just leave her still
After the sun goes down
And I smoke this cigarette
Lyle Lovett - Pontiac
“I don’t think they play at all fairly, and they all quarrel so dreadfully one can’t hear oneself speak–and they don’t seem to have any rules in particular; at least, if there are, nobody attends to them–and you’ve no idea how confusing it is all the things being alive;”
Alice in Wonderland
Probably from reading the Pipe forum.
Kevin Krell
Also inspired by the pipe forum.
Mukade
Edited several times because “Bill! Feck! Arse! Gates!”