An uncle taught me this trick when I was young -- it always amuses children, but can be a cool feat of close-up mentalism for any audience.
In this trick, you place a card flat on the back of your palm. Apparently using only the powers of your mind (look mom -- no hands!) you slowly cause the card to bend right before your audiences eyes.
This is a great close-up trick that requires no prep work.
So what is the secret to this trick? Spit. Before you place the card on top of your hand you need to moisten the back of your hand with a bit of saliva. I suggest pretending to wipe your nose with the back of your hand, covertly licking it in the process.
Tips: The warmth from your hand and the moisture causes the bend... this trick works best in warm, humid weather. Also the warmer your hand and saliva are the faster and more dramatic the bend will be.
Remember -- you are suppose to be using your "mind powers" or "telekineis" or some other BS to bend the card. Look like you are doing so, make some energy flow out of your hands, and use that premise to take breaks, lift the card up and show how it is bending. Do the nose wipe again if you need some more moisture or to blow warm breath onto your hand.
This explanation just covers the basics of how the trick works. You will need to produce your own patter.