Chris's funny relative thread got me thinking about my uncle who was into card tricks. I only remember one he taught me. It is so easy and everyone falls for it. Kids love it.
You need a standard deck of cards. Remove all the Jacks. Take three of the Jacks and tell a story about how they are Siamese triplets and every time the doctors tried to separate them, they always find their way back together. Then you say that the doctors got them apart and put one on the top floor, one in the basement and one in the middle floor of the hospital. Then there was an earthquake (cut the cards a few times as you are telling the earthquake part) Then after cutting them a few times, say that when they were looking through the rubble, they found the Siamese twins together. There will be three Jacks together.
How it works: to set up the trick, you have to have one of the four Jacks on the bottom of the deck. So, when you put one Jack "In the basement" you have those two together. When you cut the cards, the top Jack joins the other two, giving you three Jacks together. So when you cut the cards, you have to be very careful not to separate those three. The three Jacks are not the same three you started the story with, but people don't notice that. Kids really get a kick out of it. Some adults who know enough about card tricks to pay attention to suits figure it out, but some adults get a kick out of it too.