Effect: 

Magician lays out 11 cards and asks somebody to move several cards over from the right side to the left side while the magicians back is to the cards so he/she doesn't see how many. 
Then, when the volunteer is done the magician turns back around. He/she waves his hand over the cards and turns over a card. The number on the card is the number of cards the volunteer moved. 

Supplies: 

11 cards from a regular deck of 52. Take 1 joker, an ace and all the numbers up to 10. 

Secret:

Lay out the cards face down in this order: 

6 5 4 3 2 A J 10 9 8 7 (A is Ace and J is Joker). 

Remember the 7. 
Then have someone move the cards one at a time from right to left. 
Say they moved three cards (the magician wouldn't know it though) the position of the cards would be 

9 8 7 6 5 4 3 2 A J 10 
Then wave your hand over the cards and count 7 cards over from left to right. Turn the 7th card over. It's 3!
It doesn't matter how many cards they move over. 
Always count 7 cards over and it will always be the number of cards they moved. 
If they decide not to move any at all the card will be a Joker and this tells you they didn't move any at all.