There are 54 playing cards to be found throughout RAGE, if you get them all you get the Gotta Have 'Em All achievement.
Four cards are added to your deck as rewards for Jobs: Dune Buster Card (Durar's Time Trial), JK Stiles Card, Cuprino Card, and the Sally Card (Sally's Bounty). Five are part of the Starter Pack that you can buy at the shop: City Guard Card, Club Mutant Card, Mayor Clayton Card, Jetter Card, Sheriff Black Card.
Collector Card: Dan - After Dan takes you back to his place, it's on the bedside stand.
Collector Card: Grenade - Right outside the garage at the Hagar Settlement on some barrels.
Collector Card: Loosum - It's on a boulder outside Dan Hagar's door.
Collector Card: Dune Buster - Reward for Durar's Time Trial
Collector Card: Ghost Bonestick - During the Quell the Bandit Threat job, after you kill the second bandit, walk to the back of the ledge.
Collector Card: Ghost Boss - During the Quell the Bandit Threat job, after you kill the second bandit, you'll come to a room with a cube statue. The card is in the back of the room next to a stand.
Collector Card: Ghost Pistol - Inside the grindable door at the beginning (you'll have to come back).
Collector Card: Janus - During the Medical Supplies job, it's across from Janus on the couch.
Collector Card: Turret - During the Where's Juno job, after killing the first two enemies head down the stairs to the right and it's on a chair.
Collector Card: Riktor - During the Radio Tower Repair job, after you pass Juno's body it's to the left on a ledge before you go up the ladder.
Collector Card: Wasted Club - During the Find the Buggy Parts job after getting past the electric door, head downstairs, stay to the right and go up the stairs. It's around the corner on the ground.
Collector Card: Wasted Pistol - During the Find the Buggy Parts down the second set of stairs around the corner in a box near some street signs.
Collector Card: Wasted Turret - During the Find the Buggy Parts job after you beat the turret guy, head into the next room and it's in a crate to the right.
Collector Card: Mutant Scoop - During the Mutant Bash TV job, After you finish Mutant Bash TV it's on a box to the left.
Collector Card: Shrouded Minigun - During the Feltrite Crater job, when you reach the Feltrite Crater, it's in an open shipping container.
Collector Card: Sally - Reward for talking to Sally after destroying some cars for the Sally's Bounty job.
Collector Card: Slime Mutant - During the Defibrillator Upgrade job, when you walk into Dead City Center it's ahead to the left on a table with a lantern.
Collector Card: RC Bomb Car - During the Destroy the Bomb Caches job, above the hole you drive the RC Bomb Car through on the left.
Collector Card: Shrouded AR - During the Destroy the Bomb Caches job, when you get to the lower area, its down the ramp in the back right corner.
Collector Card: Shrouded Heavy -During the Destroy the Bomb Caches job, after you come out of the sewer pipe, it's ahead to the right in the smaller sewer pipe that's laying out.
Collector Card: Giant Mutant - During the Liberate Captain Marshall job, after you disable the fourth laser field, you'll enter a small room. It's in a hole in the wall that you have to crouch into to the left.
Collector Card: EMP Grenade - During the Liberate Captain Marshall job, after the giant Mutant Card, you'll be in a fight with a shield guy and then go upstairs. It's at the top of the stairs to the right on a shelf.
Collector Card: Marshall - During the Liberate Captain Marshall job, when you're heading downstairs in the cell block, there is another set of stairs to go down. It's in a locked room down there.
Collector Card: Shield Guard - During the Liberate Captain Marshall job, after you part ways with Marshall a door will open, it's on a box to the right in that room.
Collector Card: Elizabeth - During the Liberate Captain Marshall job, when you get back to Wellspring, head in the back of the Second Chance bar and go through the door. It's halfway down the stairs.
Collector Card: Drone - During the Lost Research Data job, when you get back to the escalator in Dead City, head down, take a right and it's on a table.
Collector Card: Authority Mutant - During the Gaining Influence job, after talking to Captain Marshall, head in the room to the left, its on a tray.
Collector Card: Advanced Sentry - During the Gearhead Vault job, after you kill the large guy head up the ramp and it's in a car to your right.
Collector Card: Gearhead Shotgun - During the Gearhead Vault job, after you turn off the fire door, go in the next area, it's to the far right on a ledge.
Collector Card: Gearhead Jet - During the Gearhead Vault job, on your way out through the hole that gets blown in the propeller room, its to the left behind the counter.
Collector Card: Portman - During the Abandoned Distillery job as your walking through the caves to the distillery, it's on a box on the right.
Collector Card: Jackal Crossbow - During the Ark Equipment job as soon as you enter Jackal Canyon, its up to the left on a box.
Collector Card: Jackal Club - During the Ark Equipment job after you cross the first bridge, it's on the table to the left before you pull the switch.