Dataset
MLB Gameday: full Play-by-play, Box Score, Pitch and Pitch Trajectory
MLB Gameday provides data files describing every pitch for most games, beginning in the 2007 season. The XML files are available from their Gameday server.
You might enjoy
- Alan M. Nathan’s description of the gameday fields
- Mike Fast’s many useful articles
- John Walsh’s strike zone exploration at the Hardball Times.
This diagram of pitch trajectory fields might be helpful.