Hard, but works very well.
Have one person defend. Start with the ball in one hand. Once the defender moves his feet, crossover. Repeat until defender's feet cross.
To practice it, have the defender only get in the way, not try to steal it.
Do it as fast as you can.
Using both hands, crossing over quickly.
This basketball drill is licensed under a Creative Commons License. This drill is from Pål Degerstrøm at www.degerstrom.com/basketball.