you assign an exercise for every suit or if your a beginner you can do black/red. flip over a card, do the prescribed reps for that exercise and repeat with no rest until the deck is complete. check out ross enamait's article on it:
Deck Of Cards
I get a lot of my conditioning stuff from him.
Some favorites for the exercises are; burpees, mountain climbers (x 5 on card), jump rope (rope turns x 10), db swings, horizontal pull ups, regular pull ups/chin ups, pushup, bw squats, box jump, split squat jump, skiers...you can basically do anything! trust me, no rest will give you a great workout.
oh, and make the joker (if you have one or two in the deck) something really hard like 1 minute sprint on treadmill or bicycle.