There is of course Sidney Harris' famous "Then A Miracle Occurs" math cartoon:
(You can find more of Harris' here .)
Another favorite is the T-shirt that says, "They Told Me There Would Be No Math Involved". And who can forget the statement, "There are three kinds of people in the world. Those who are good at math and those who aren't."
All this however is just a lead up to this outstanding, brand new math joke I heard at work last night.
"What does a mermaid wear?"