Snyder
http://www.snyderbaseball.com/directions.shtml
and Pippen
http://www.playersedgetraining.com/index.html
have coached our best pitchers - results show.
There's another whose name is escaping me - I'll post that name when I ask the mom. I'm results oriented - not hype/marketing. This recommendation comes from watching the pitchers who are successful and asking "Where did they learn how to do that?" A couple pitchers have been to both of these men and recommend both.
I can't speak from son's personal experience - yet - but will say that I've spoken with Pippen and was very impressed with his philosophy and emphasis on injury prevention.
These guys aren't cheap.