Essentially anything at all uttered or written by Bill Bryson, Douglas Adams or Stephen Fry really. One I'm particularly taken with at the moment is:

"A sign in the yard of a church next door said CHRIST IS THE ANSWER. (The question, of course, is: What do you say when you strike your thumb with a hammer?)" - Bill Bryson (The Lost Continent)

Otherwise another particular favourite:

"Plato is my friend — Aristotle is my friend — but my greatest friend is truth." (Isaac Newton)

There are lots of quotes I like and I have trouble keeping track of them all!