I basically just Googled them, but I like this one:

"A library is a hospital for the mind."

There are also a bunch in Ray Bradbury's Farenhenit 451 that I love. I'm not sure how much sense they'll make to someone who hasn't read the book, but here's my personal favorite:

"There must be something in books, things we can't imagine, to make a woman stay in a burning house; there must be something there. You don't stay for nothing."