Hearts

Case's Ladder
Listing of multi-player leagues.
http://www.casesladder.com/browse.php?game=Hearts

My League
Listing of user-managed multi-player leagues.
http://www.myleague.com/cgi-bin/ladder/browse.cgi?service=Hearts&my=1

Nova Hearts
Standard four-player game. Includes rules and FAQs.
http://vex.net/hearts/hearts.html