A lecture about English
A linguistics professor was lecturing to his English class one day. "In English," he said, "A double negative forms a positive. In some languages, though, such as Russian, a double negative is still a negative. However, there is no language wherein a double positive can form a negative."

A voice from the back of the room piped up, "Yeah, right."

A visitor from Holland was chatting with his American...
A visitor from Holland was chatting with his American friend and was jokingly explaining about the red, white and blue in the Netherlands flag. "Our flag symbolizes our taxes," he said. "We get red when we talk about them, white when we get our tax bill, and blue after we pay them." "That's the same with us," the American said, "only we see stars, too."