I've been playing Out of the Park Baseball for the past 3 years over 4 different versions and like to let people know about what I consider one of the best sports games on the market.
Anyway, the latest version is now available for pre-order over at http://www.ootpbaseball.net/
OOTP2007 is a simulation game that lets you create your own baseball universes, take control of a team from the front office perspective, and then simulate your way to baseball bliss. You can play solo or join one of the many online leagues to play against other live owner/GM's. The user support is tremendous and the forum community is highly active. I encourage you to go check it out.