Urban legends are a kind of folk tales of our times. Those who tell them believe that they really happened. They don't have to be false, but they are often exaggerated or distorted. Many of them originate in our fears, others are just made up as a good joke.
One of the most popular is the story of a vanishing hitchhiker. There even exists a whole book on it. Probably you all know the story - somebody is driving when he sees a lone figure in the middle of the road. He gives this person a lift and at some point the hitchhiker vanishes. There are many variants to this story. Sometimes the hitchhiker leaves an item in the car, and when the driver wants to restore it, he learns that the owner is long dead. Sometimes the hitchhiker tells the driver not to drive this or that road, and the driver later learns about a horrible accident that happened there, so if he took the road, he would probably be killed there.
Many other urban legends may be found on the web. I suggest starting with http://en.wikipedia.org/
