This is a fun collection of mathematical quotations compiled by a professor at Trent University:
http://euclid.trentu.ca/math/sb/misc/quotes.html
The list includes some classics, such as the following famous remark from John von Neumann:
“In mathematics, you never understand things; you just get used to them.“
I also like this quote, attributed to Hungarian mathematician Raoul Bott:
“There are two ways to do great mathematics. The first way is to be smarter than everybody else. The second way is to be stupider than everybody else — but persistent.”
To add a favorite recent quote of mine to the list, a teacher was discussing how she used the idea of friendly numbers to help her quickly calculate in her head. But while explaining the process, she warned us to be careful: “Remember, what’s friendly to me may not be friendly to you!“.
