Cards are something I've really gotten into recently.  I've always loved to play, but card designs really are intriguing and often amazing.  Here are a few of my favorites and some links to more.
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< Classic Ace Flyer Playing Cards
A special edition of classic Bicycle playing cards in black with a Grim Reaper Ace.  ^
Truly, "Bicycle" cards, made by the same.  ^
Some really cool Japanese playing cards.  Not sure if they're vintage or not, but either way, they're awesome.

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< A set by the card company Kem.  The style is Arabesque.  Kem's cards hold up better than most cards out there, and they make a lot of awesome designs. Click here for some more Kem cards and check out how awesome these cards are!
Kardwell Int'l
A good selection of classic playing cards
Vintage (practically antique) Mohawk cards in EXCELLENT condition.  Very detailed.  (Below)
Some fun cards from the Tabasco Company, vintage.
Spotter cards from World War II and the Korean War era designed for Air Force and Navy.  These were actually commonly used by all the Armed Forces, and they definitely worked for their purpose.