It's been a while, but I found dribbling two balls at the same time (alternating and in unison) to be effective. Of course while you are doing this you should run, change speeds, even go side to side a bit and also change how high off the ground you are dribbling.
It isn't necessarily going to give you killer 'handles', but you will become much more adept at keeping control over the ball at all times when multiple defenders are around you since it is a practice of constantly having to pay attention to your dribble.