Great game, but hard.
http://www.gamespyarcade.com - Gamespy Arcade, for multiplayer, stat tracking, gameplay time tracking, chat, files, joining games, hosting games, and creating a server.
http://www.comrade.gamespy.com - Gamespy Comrade, for multiplayer, stat tracking, gameplay time tracking, chat, and files.
http://www.xfire.com - Xfire Incorporated, for multiplayer, stat tracking, gameplay time tracking, chat, files, and in-game messages.
http://web.archive.org/web/19990424145410/http://www.xfire.com/ - Xfire, required for multiplayer with EA Matchmaker, equivelant browsers may also work.
http://web.archive.org/web/20011211174541/http://www.ea.com/worlds/games/sub_command/home.jsp - MatchMaker, for multiplayer and chat.
http://files.filefront.com/xfire_gamesini/;6694016;;/fileinfo.html - Xfire Games, required to play Sub Command on Xfire.
http://www.hamachi.cc - Hamachi, for multiplayer, file transfers, and chat.