The following are some websites found that may provide useful information.
General Sports Information:
Baseball, Basketball, Hockey and Football Online Statistics Databases
Ballparks.com
Journal of Sports Economics (abstracts of articles)
Links to all sports
The Sports Economist
Professional Baseball Information:
Baseball Economics Resources
Baseball-Links.com – All Sorts of Baseball Links
Baseball-Reference.com – Major League Baseball Statistics and History
Baseball Think Factory
Business of Baseball – The Baseball Archive
Major League Baseball : Official Info : Home
Major League Baseball : Official Info : Official Rules
The Business of Baseball
Professional Basketball Information:
Basketball-Reference.com – Professional Basketball Statistics and History
BasketballReference.com – NBA Basketball Statistics, Draft, Awards, and History
NBA data
The Business of Basketball
Professional Football Information:
Pro Football Reference.com
The Football Database
The Business of Football
Professional Golf Information:
ESPN.com – GOLF – Statistics
PGA
USGA
Professional Hockey Information:
NHL Stats Database
The Business of Hockey
The Internet Hockey Database