I also attended a talk a few years ago by an IM. In question time someone asked him if he believed in Queen sacrifices (dumb question!). The IM replied said, "Yes, every opportunity I can get. Just so long as it is my opponent's Queen."
What is your favorite chess quote?

Emanual Lasker "By what right does White, in an absolutely even position, such as after move one, when both sides have advanced 1. e4, sacrifice a pawn, whose recapture is quite uncertain, and open up his kingside to attack? And then follow up this policy by leaving the check of the black queen open? None whatever !" - on the King's Gambit

"Chess is mental torture." - Kasparov
"When I asked Fischer why he had not played a certain move in our game, he replied: Well, you laughed when I wrote it down." Mikhail Tal
Both Emanuel Lasker:
"On the chessboard lies and hypocrisy do not last long."
and
"In mathematics, if I find a new approach to a problem, another mathematician might claim that he has a better, more elegant solution. In chess, if anybody claims he is better than I, I can checkmate him."

I always liked Tarrasch's "The threat is worse than the execution.", which I have found useful in settings other than chess.
Today it's:
[pfren]
Your style is making lots of mistakes, play classical king pawn openings and follow opening principles, don't learn openings.
[/pfren]
Thanks Scottrf!

When a match is over I forget it. You can only remember so many things, so it is better to forget useless things that you can’t use and remember useful things that you can use. For instance, I remember and will always remember that in 1927 Babe Ruth hit sixty home runs. – Jose Raul Capablanca

one of my favourite quotes is also this one by Tal :
You have to take you opponent into a dark forrest were 1 plus 1 is not 2 and where the path out is only wide enough for one person.
This one's great.

"Let us say that a game may be continued in two ways: one of them is a beautiful tactical blow that gives rise to variations that don't yield to precise calculations; the other is clear positional pressure that leads to an endgame with microscopic chances of victory. I would choose the latter without thinking twice. If the opponent offers keen play I don't object; but in such cases I get less satisfaction, even if I win, than from a game conducted according to all the rules of strategy with its ruthless logic."
-- Karpov

"Tactics is knowing what to do when there is something to do. Strategy is knowing what to do when there is nothing to do."
Savielly Tartakower

Fischer wanted to win a game against Woman World Champion Nona Gaprindashvili without one knight.
Tal commented on this: "Fischer is Fischer but knight is a knight!"
This story was told by Lothar Schmid (arbiter in Buenos Aires and Reykjavik):
Normally Fischer wanted to have best playing material possible. The pieces and the board had to be without any reflexes of light and also the light should be optimum ...
However in one game the electricity failed. Schmid had to stop the clocks. Fischer had to move - he was using this whole 20 minutes thinking while the electricity was fixed again. (Eventually there he found a winning combination.) *rofl*
I think it was Alkehine who was sitting at a Parisian cafe table that had a chess set. A stranger came up and challenged him to a game. Alky agreed and promptly removed his Queen's rook. The stanger objected offended and protested, "Who do you think you are, sir, to give me a rook start? You don't even know who I am." Alky replied, arrogantly as usual but accurately, "If I couldn't give you a rook start I would know who you are."