New Super Mario Bros Star Coin Locations
I got a bit bored with not being able to add tons of new content, so here is a full checklist to the star coin locations in New Super Mario Bros. This may help if you are trying to get three stars.
World 1
Level 1
To the left of a brick platform after a pipe Inside the cave near the exit pipe Under some bricks in an alcove
Level 2
In a alcove, in plain sight as you go through the first area of the course Inside an odd brick structure In an alcove near the secret exit
Level 3
Go upwards with springboards, and off a bouncy platform. It should be a bit upwards of you. Follow the trail of coins to reach this coin Above the mushrooms bouncing up and down
Tower
Go up the tower until you reach a giant Dry Bones. It is to the right, in a small area. When you see a pipe, go to the right, and climb the spiked platforms. It is above the next blue platform Wall jump up the shaft where the first green pipe would shoot you and enter a door. It is in the air in this secret room
Level 4
When you see a hollow in the ground, and a mini pipe, hit the right blocks for a mini mushroom. Go in the mini pipe. It is in that room. Go to an area with a koopa and a structure of blocks. See the green pipe? Go through that, and it is on a high platform in that secret room. After the structure, and a goomba pipe from the sky, slide down the slope, and under an overhang to reach the final star coin
Level 5
In the air above the bouncy mushrooms After the first hanging platform, on a high mushroom In the middle of a set of coins in a secret area accessed by entering the first pipe you see.
Level A
Near the top of the area near a green pipe Go up that green pipe, and the coin is on the highest platform in the secret area On a high platform after the halfway point, pipes and a switch
Castle
In the area with rising and sinking spiked walls, one opening will have the star coin in On a sinking platform after the halfway point and some ropes Late in the level, there is a pipe in the ceiling. Inside the room is the final star coin
World 2
Level 1
In the air near the third Pokey In the air near a pokey on a moving platform On a platform in the second area with moving platforms and pokeys
Level 2
In the sky, so ride a Lakitu cloud to the coin Under a ledge near the start High in the air, in a secret room accessed via a pipe
Level 3
When you first reach a breakable pad, wall kick up to a higher ledge/alcove area In between some movable platforms near the first piranha plant After the large piranha plant, in an alcove to the left in the larger room near the end of the level
Level A
In an alcove in easy sight Under a high ledge near the end pipe In a secret room after the red pipe and before the secret exit
Level 4
Above the first green pipe, in a visible alcove area In the area where the secret pipe takes you Between the two Hammer Bros platform
Tower
In the second area, walk kick to a door on a high ledge to the left. Go through the door, and use wall kicks well to get to the star coin In an alcove after the second spinning platform in the second area In the final area, use the final switch to make platforms appear. Go all the way to the pipe, wall kick up the side of it and hit a switch. Use the newly found platforms to reach the final coin
Level 5
Above a column of bricks near the start Hit a switch, and use the solid bricks to get to the star coin near the fire snakes. Go under the right wall near the Boomerang Bro, and go to the right to enter a cave. Ride the blockhopper to the coin
Level 6
To the left of the first moving up and down platform When another platform appears above the first, ride that and jump to reach the coin Above the final moving platforms
Castle
In an alcove where the fifth small spiky ball rolls down (not near a door, that one's a pit!) In an alcove near the third/fourth Bullet Bill cannon In the Mini Mario only area under where some spiked balls roll down steps.
World 3
Level 1
Between a yellow pipe and a green one Enclosed by some bricks Inside a room entered via a pipe
Level A
Under a ledge, there are some blocks and a skuttle bug. Make it break the bricks to reach the coin High above a koopa on a barrel Enter a green pipe in the ceiling, and it is above the water in the new area
Level 2
Go down the second yellow pipe, and the star coin is above the second mushroom platform On a high up green ledge after the hanging platforms Above the final platform which moves horizontally
Tower
In a hidden alcove to the left of the main path near the start Near the door in the secret area entered via a door to the far top right of the second area In the second area, above a platform with a koopa
Level B
In between two pipes, under a row of blocks In an alcove to the left of a red block in the ceiling Under an L shaped green pipe
Level 3
When you reach a set of pipes spraying strong currents out a right wall, drop down the canyon type gap and it is in an alcove to the left, near a blooper and pipe At the long row of pipes, down the third pipe in the secret room with bloopers and blooper nannies Down the final large gap. Be careful, as when you get it, four bloopers appear.
Ghost House
In the second door, in the room it leads to, above some splumpkins Go up the second set of stairs, then up the stairs to the right of them and you'll see it. In the final room, use the blue shell to break the blocks near the exit door to reach an area with the final coin
Level C
Under four platforms in a row which fall away when you stand on them Under a gap between two grassy platforms where there is a lone platform in the gap Go up the red pipe at the end of the first area, and you will drop onto a platform with the coin
Castle
You can see it in an alcove to the slight left of where a spiked pillar crashes down Above the pit of spikes after two Whomps. Slide through a small gap after the boss door, and you should be able to see where it is
World 4
Level 1
Easily found floating above two spiders When you ride Dorrie, between the second and third spider you come across There is a part with a few spiders, three rows of donut platforms and a set of wooden blocks. Under the wooden blocks, on the middle row of donut platforms is the coin
Level 2
Above a lone block which is above a purple mushroom platform Between a purple mushroom platform and a green one, shortly after the first star coin
Level 3
After the first mega unagi (eel) attack, you will see it under an overhang When unagi attacks for the third time, it is between two smaller eels Go down the fifth pipe (second green one) when Unagi attacks for the fourth time. It is in the room, guarded by smaller eels
Tower
Go to the other site of the fences, and to the left at the first split. You should see the star coin to your left When you see three amps beneath a ceiling, between the second and third amps to the right Go right after the amps, and you should find the coin hidden away
Level 4
When you see a gap and a platform to the right of it, on a secret platform under the top one, guarded by a wiggler When you reach a block with a set of random items, climb the vine, go to the left and it is high in the air, above a wiggler To the left of the first set of two very thin pipes
Level A
After the area with three red koopas, past the halfway flag, there is a rotating platform with some paratroopas. It is in the air When you see a vine, swing up to a pipe. Go in, and it is the middle of the brick structure with many koopas in the secret room When you see three pipes before dry land, all with piranha plants in, go down the green one. It is in the secret room
Ghost House
Enter the first door, hit the switch to make blocks come down and stand on one to be pulled through the ceiling. The star coin is to the right of where you end up In the room after, hit the red switch and enter the door. In the room you end up in, hit the next switch, wall kick up between two columns of red blocks and you will end up in a secret area with the coin Jump on the pipe as mini Mario to get out the room, but don't go in. Wall kick off to the right to land on a ledge and go up to find the final star coin here and the secret exit
Level 5
After the halfway flag, you will see it enclosed in a prison of blocks Hit the bob-omb after the second see saw to blow a hole in the set of blocks, and go up there for it When you see a pipe blocked by brick blocks, blow it away and go down. It is in the room
Level 6
On a platform with two koopas The next two are further in the level
Castle
On a platform above the area with the Thwomps Under the platforms the mega thwomp destroys On a ledge in the final area of lava
World 5
Level 1
Above a lose section of snow, high above a snow pit and near a tree Above a snow pit near a hopping paratroopa In the air in front of a snowball spike enemy
Level 2
In an alcove above a brick ledge Between two columns of blocks, where some spiketop enemies are moving around Go up a yellow pipe after the piranha plants in pipes, and it is by the end pipe in the secret area
Level A
Under an alcove, near a red switch On a mushroom platform between two higher mushrooms When you see a lone brick block floating in the air, hit it from below and climb the vine to a secret area. Hit the switch, and use the spring to land on the high platform with the star coin
Tower
The coins are easily seen and gotten as you go up the tower on the elevator. Just watch out for spiky balls!
Level 3
In an alcove in the area with the snailicorns, above some bricks In an alcove near the end of the snailicorn area, where some coins are going upwards Become mini, drop down the second or third gap near the start and enter the mini pipe. It is probably in the secret area
Level B
When you see a koopa hopping across an ice platform, it it under the ice platform When you reach an area with a blue switch, hit it and run left, jumping the gaps and through the coins at the end to find the star coin. After the blue switch, it is in the alcove with a snailicorn
Ghost House
When you reach a Broozer (boxing ghost), behind some bricks, get it to smash them, then smash those below. Go through the gap and wall kick upwards to reach the ledge with a star coin When you see a door on a ledge, high up to the left, enter and it's in the secret room In the secret elevator area, go off the elevator to the right as soon as you see a gap, and it's in the secret area.
Level C
Surrounded by bricks after the second broozer In an alcove to the right of the second set of moving platforms When you reach an area near some steps with two layers of brick blocks, smash the top ones and thne hit the one on the bottom layer which is to the right for a vine. Go up, and it's in the secret area.
Level 4
When you first reach solid land, jump to the higher ledge for the star coin As soon as you reach th ered mushroom going up, after the first star coin, grab the koopa shell and throw it to the left along the higher ledge. Or run and get it quickly before the coin goes off screen. You will see it after another red mushroom. Quickly run across the mushroom to the coin before the mushroom goes up too high
Castle
On a ledge under a conveyor belt On an alcove high under some conveyor belts with Dry Bones enemies and a springboard In a secret area under the boss door.
World 6
Level 1
In the air above a ledge after the first area where you walk on ropes When you first reach the area where you have to walk kick to go further through the level, wall kick to the left and it is in an alcove Under a tightrope near the flag
Level A
In the air after a tornado When you see quicksand going down a gap between two columns, stand in the sand to enter a secret pipe. The coin is in the secret room where you end up, in an opening in the right wall Go down the yellow pipe, and it is in the secret room near a mega piranha plant
Level 2
When you see a lone block floating, jump up around it to make more appear. When a vine grows upwards, climb it, jump across, hit the block for a switch, hit the switch and jump across the winged blocks and platforms to the coin. Keep going right and it is in an area high in the rock In the gap under a log where many spinies walk across
Tower
In an alcove after the third or fourth pile driver smashes across the screen When you reach a door, go in, and it is on one of the platforms Well, you wall kick to enter a door on a ledge above the boss door, and it is in the middle of the room shown on the below map:

Level 3
In the air after the first swinging block Go down the third pipe in the pipe area and it is in the secret room Between two high pipes after the pipe area
Level 4
In the first area you can wall kick into to After the red switch, on a high ledge to the top left In the final secret area
Tower 2
On a conveyor belt to the right, near a spiky wall In a gap in the platform where spike tops walk around constantly Go across the rope, and you will go into the star coin
Level 5
Near the roof, guarded by two deep cheeps Gop up the yellow pipe, and it is in the secret room, guarded by Deep Cheeps Go down the whirlpool surrounded by bricks, and the star coin is in the secret room
Level B
In the air, under a green paratroopa. Go into the second green pipe, and get shot up to the higher ledge. The star coin is in the air to the right, above a green paratroopa. Nearer the end of the level
Level 6
Far to the top left in the first area of the level is the first star coin. To the high left, above a Chain Chomp In the second area, go in the green pipe. The coin is in the secret room
Castle
Above the lava between two moving platforms Under a stone platform between two moving platforms At the end, go above the final part of the ceiling and keep going right, past the boss door to the coin.