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."

Bad News and Good News
Jill phoned her husband, John, at work for a chat. "I'm sorry dear," said John, "but I'm up to my neck in work today. I don't have time to chat."

Jill replied, "But I've got some good news and some bad news for you, dear."

"OK darling," said John, "but as I've got no time right now, just give me the good news."

"Okay," agreed Jill. "Well, the air bag works...bye!"