Official Sports Rulebooks

NFL
http://www.nfl.com/rulebook
NBA
http://www.nba.com/analysis/rules_index.html
WNBA
http://www.wnba.com/analysis/wnba_rules_regulations.html
NHL
http://www.nhl.com/hockeyu/rulebook/
WTA
http://www.sonyericssonwtatour.com/global/pdfs/shared/thewtatour/officialrules/rules.pdf
ATP
http://www.frankymoser.de/ATP_Rulebook.pdf
MLS
http://web.mlsnet.com/about/league.jsp?section=rules&content=overview
MLB
http://mlb.mlb.com/mlb/official_info/official_rules/foreword.jsp
PGA
http://www.usga.org/playing/rules/rules.html
LPGA
http://www.lpga.com/content_1.aspx?mid=8&pid=109
X-Games

Olympics