The United States Chess Federation
http://www.uschess.org/

FIDE
http://www.fide.com/

The International E-mail Chess Group
http://www.iecg.org/

The International E-mail Chess Club
http://www.chess-iecc.org/

PGN Software
http://pgn.freeservers.com/

Chess Software from ChessCentral
http://www.chesscentral.com/