Baseball Prospectus
http://www.baseballprospectus.com/

The Hardball Times
http://www.hardballtimes.com/

Baseball Think Factory
http://www.baseballthinkfactory.org/

Baseball America
http://www.baseballamerica.com/

Down on the farm
http://sports.espn.go.com/espn/archive?columnist=sickels_john&root=mlb

Minor League Baseball
http://minorleaguebaseball.com/