I learnt this neat little trick when I went to a party being thrown by Hastings Community Circus. It involves a bit of contact juggling so this trick is easier if you use solid juggling balls which will roll over your hand nicely. If you've done a bit of contact before skip straight to the third paragraph, if not read on.
Hang one arm straight down by your side, then bend the elbow so that your hand is pointing straight up. Now bend your wrist back & hold your hand open so that your palm faces straight up & your fingertips point out to the side, as if you were waiting tables & holding a tray of drinks. Now place one ball on top of that hand, just above the palm on the fingers. Don't grip the ball at all, just let it sit on your hand. Now give a gentle upward push with your arm & at the same time bend your wrist forward to make the ball roll up your fingers. When the ball reaches the top of your hand let it roll over your fingertips & down onto the back of your hand, move your hand down until it is horizontal & make the ball come to rest in a Fork catch. This takes a lot of practise to perfect.
Hold your hand out again & this time place two balls on top. Place one on the fingers as before & one in the centre of the palm. Again without gripping the balls with your fingers at all, turn your hand over just like before, using both your forearm & your wrist to keep the motion smooth. Focus your attention entirely on the topmost ball, the ball resting in your palm should simply fall into your empty hand. Make the other ball roll up & over your fingers onto the back of your hand into a Fork, then dip your fingers down slightly & push up with your hand to flick the ball up & over to the other side. Stop with both balls in the other hand.
Now take all three balls, hold two in the palm of one hand as before & hold the third in the other hand. Turn the hand with two over just as you have been practising. At the same time as you flick the topmost ball up, throw the third ball underneath the ball that was tipped out of your palm. Catch the tipped ball with the same hand & Claw catch the third ball with the other hand & start juggling or stop again on the other side.