Harrington states that
"small ball is a style based on making small moves at pots, blending probe and continuation bets, to pull down pots cheaply without much of a hand."
Here is a series of videos with Negreanu "teaching," someone smallball:
http://www.youtube.com/watch?v=PdJVLZHh1Fo
http://www.youtube.com/watch?v=kxlujfwUUh8
http://www.youtube.com/watch?v=2D9aJhO9QiQ