Dvorak is a card game where all of the cards start out blank; players choose a theme, make up enough cards to get started, shuffle and deal, then add further cards to the game as the game progresses. It provides you with enough rules to start a game, but leaves the theme and the depth up to you.
You can use it as a skeleton for making a solid and standalone card game, you can play it as an experimental or cut-throat NomicGame, you can use it to kill half an hour drawing silly pictures and forcing your friends to make drinks, you can throw together an amusing card game based on your favourite film or sport or in-joke - it's blank cardboard, it's fairly multipurpose.
You can also play the games that other people have come up with, over the years - just pick something from the Deck Archive to print out and cut into a deck of cards, or play the game online.
1000 Blank White Cards (http://www.geocities.com/nconner23/bwcards.html) is a less strategic, more artistic forerunner.