A number of baseball organizations have their rules listed.  MTS gave you the site for the pro rules.  The NCAA, USSSA, and Dixie also provide theirs, free of charge:

http://www.ncaa.org/library/rules/2007/2007_baseball_rules.pdf

http://www.dixie.org/AssetFactory.aspx?did=336

http://www.usssa.com/usssa/usssa-general/2007BBBylaws.pdf

Little League does not put its rules on their website.  NFHS (high school) does not either.  PONY used to, but not anymore.  You can still find older versions of the PONY rules.

Manny Aponte