Those ordering the Collector's Edition of Fallout: New Vegas already know about the deck of playing cards included.
However, until FONV comes out, you can play the card game Caravan with normal cards featuring kings and queens.
According to a post over on IGN, Caravan, a mini-game for gambling found within New Vegas and the CE cards, as we know, contain an illustration of characters and factions found in the game.
So, to get you pumped, Obsidian and Bethesda have released a rules set, along with instructions on how to play this head-to-head style of Blackjack requiring at least two decks of cards.
The rules and instructions are quite detailed, so it'd be best to check it all out in the link above. We'd try to explain, but we get confused playing Solitaire.
Fallout: New Vegas releases on October 19 in the US and October 22 in the UK for PC, PS3, and Xbox 360.