Eddie Joseph's Mystic Fifteen

Effect
You have a spectator count 15 cards from any deck of cards and shuffle them. He is then told to deal the 15 cards into three piles of five cards each. You now ask him to pick one of the three piles and mentally select a card from it. Once he has a card in mind, you ask him to shuffle the cards he holds, so he loses track of his card.

You now pick up the remaining two packs - holding one in each hand. Holding out your left hand, you have the spectator to place his packet on top of yours. As soon as he does so, you immediately place the remaining packet in your right hand on top of the other cards to "bury" his card somewhere in the middle. At this point, you take a moment to reinforce the fact that, your helper has a card in his mind but is not aware of its location and you know neither the card he is thinking of nor its location.

The packet of 15 cards is now re-dealt - this time into five piles of three cards each. Your helper is asked to look through the piles and find the one that contains his card and place all three cards in his pocket.

Although you cannot see the face of any card, you reach into his pocket and remove two of the three cards. You ask the spectator to name the card he was thinking of and then, bring out the remaining card in his pocket. It is, indeed, his mentally-selected card!

How it works
Ask your helper to deal 15 cards into three piles of five cards each. Have him pick up any one of the three and mentally choose a card. Next, have him shuffle his packet of five cards. Pick up the two remaining packets, one in each hand, and have him sandwich his packet between them. You can false shuffle the cards at this point by milking them one at a time from the front to the back. This reverses the order, but leaves the set-up (for our purposes) intact. You now deal the 15 cards into five piles of three. Make sure you deal a complete row first (ie. 1-1-1-1-1 followed by 2-2-2-2-2 and finally 3-3-3-3-3. The 2s are the five possible cards the spectator could have chosen, since they are the five cards from his original pile. Back to the handling. The spectator locates the packet with his card and pockets it. No matter which card he chose, it will ALWAYS be the middle card of the packet he pockets. So all you have to do is remove all of the cards except the center one. The strength of this effect is that you never need see the cards and the fact that the spectator gets to shuffle the cards, so play up those aspects.