Card Games
Blackjack Doc - http://blackjackdoc.com/
Provides free games as well as a strategy guide for playing Blackjack.
Invented Card Games - http://www.pagat.com/invented/
Index of newly created games played with existing cards.
Shogix - http://www.shogix.net/
French card game. Site provides basic information on the game as well as rules and advanced strategy tips.