Another one of the throwing drills at Coach Griffin's Elite Catching camp (and on his DVD) is the throw and hold (or something like that) where after you throw you "stick the landing" i.e. balancing on your front foot with you back foot in the air. By doing this, you keep from falling off to one side and get your weight and throw going more forward. This drill can be done while warming up (as can your receiving drills, glove-hand exchange, footwork, etc.).
Here is a youtube of my 13yr old doing another drill but concluding with the stick and hold
http://www.youtube.com/watch?v=nNW1PBz9HJ4(Note: as you can see my son didn't do it very well as his head still went to the side and causing him to be off balance. He did get a little better at it later, but you really need to be over your front foot with you back leg up in the air behind you...kind of like a figure skater)
Hopes this helps.