I would say that a baby can "dribble", this is the physical action when some spit or saliva is falling out of a babies mouth (for example) of which the baby has no control. To "drool" can be the non literal (non physical) action of some guys "drooling" over some very attractive ladies. This is whereby they are lusting after the ladies but they are not literally"dribbling" from their mouths. In my mind that is the main difference between these two words.

I agree with Greg, except that we never say our baby dribbles - even though that is what he is doing. We just say he's drooling...A LOT! :) You can also dribble a ball, and it means a very different thing (bounce repeatedly). So it depends on context.