Fable III

Here is another video solution, for every area an own video.
The quality of the video is not the best but you can follow him very good (no jumps, he is runnig all the time)
Credits for the video goes to: 360addictsRUs (Youtube)

The last videos are for the gold keys
Credits for the video goes to: TehVGGs (Youtube)

Here is a great video guide by Achievement Hunter.

Note: NONE OF THESE ARE MISSABLE. You can simply go back and grab a key whenever (You don't HAVE to grab them on the way through the story)

Read the comments for a couple extra tips if your stuck.

These are the four gold keys that THE IRISHMAN 35 guide is missing

Gold Key 1: Driftwood
You will first need to go to Millfields and complete the 'Restoration' side quest by paying 750 gold to repair the bridge to Driftwood. Once in Driftwood, locate and complete three more side quests (An Island Getaway, Pest Control, Giftwood for Driftwood) that will grant you access to the coastal islands. On the island you'll find a flit switch which you can follow and shoot the switch as it leads you up the mountain. At the top you'll warp to the Gold Key.

Gold Key 2: Mistpeak Valley
Chillbreath Cavern is your goal, located on the side of the map away from the Demon Door (two other caves are near the door). Once in the cavern, follow the main path uphill until you find an exit and follow it out. The same general direction will lead you down a hill where the Gold Key awaits in the ruins.

Gold Key 3: Aurora - The Veiled Path
Find the Enigma area of The Veiled Path and shoot the flit switch to get into the next room. Use the Fireball spell to light the torches you see to proceed. In the next area with colored floor panels and flames on the wall. The flames reveal the pattern to step on the panels: Yellow, Blue, Yellow, Red, Blue, Red, Blue, Red. Once completed, the next door will reveal the Gold Key.

Gold Key 4: Aurora - Shifting Sands
Complete the 'A Key To A Greater Key' in Aurora's city. Once complete, the guy who gave you the quest will sell you a key for 4,000. After buying the key, head to Shifting Sands and run across all the sand dunes. On the other side, hang a left at the cliff face and locate a path near the ruins. You'll find a door that requires a key, the one you just bought. Fight off some enemies on platforms to reach the Gold Key.

Found this info on http://www.thehdroom.com/news/Fable-3-Gold-Keys-and-Doors-Lo...

Catacombs
Silver Key #1
This key will be found down the steps from where you first enter the Catacombs from the Castle and where you found the Guild Seal. Keep going down the path to the overlook point and then turn left near the ruins.

Dweller Camp
Silver Key #2
When you return to the camp you will find that the gate to Sabine’s inner camp is open. Enter this area and then look behind the wagon on the right to find the key.

Mistpeak Valley
Silver Key #3
The key is behind the pile of logs near the clear area on the banks of the lake. This is downhill from the Demon Door and not far from the Mercenary Camp.

Silver Key #4
Head to Mistpeak Monorail Station entrance and go up the hill on the right. There will be a small trail here that fades away, continue going between the rocks and the trees to the ridge to find the key.

Brightwall Village
Silver Key #5
You will find this key beneath the small stone archway that is near the house outside of the village. It is also across the main bridge from Brightwall.

Silver Key #6
You will find this key to the left of the entrance to Brightwall Academy. It will be behind the rocks between the Academy and the house nearby.

Silver Key #7
You will find this key behind the Bernard and Patsy’s House which is near the chicken coop. You will need to circle around their house to find it.

Reliquary
Silver Key #8
You will need to go to the area further than the circular vault door that you must open with a magic spell. Then use the Fireball spell to light the six cauldrons by the locked door to be able to grab this key.

Silver Key #9
Head to the room with the grid of floating platforms and chests and push the lever in the temple. This will make a staircase rise near the rocky ledge with the chest on it. Head up the stairs to a small tomb and here you will find the key near the sarcophagus.

Mercenary Camp
Silver Key #10
You will find this key under the watchtower at the top of the hill near the wolf cages. This is the last watchtower before the Saker’s inner sanctum.

The Hole
Silver Key #11
You will find this key behind the rack of barrels along the far wall when you follow the cart tracks down the hill from the monorail wreckage to the storage area.

Silver Key #12
You will first need to enter the Millfields Monorail Station and then go into the southeast corner of The Hole. Then climb the stairs to the monorail platform to find the key at the far side.

Silver Key #13
You will need to use the Technician’s Key to unlock the gate beyond the monorail wreckage and then follow the upper path to the ledge above the arena. Here you will see the key where you have to fight the hobbes.

Mourningwood
Silver Key #14
You will find this key in a bunker but first you will need to detonate the barrel a wooden barricade that is blocking the entrance to the bunker. You can either shoot it with your gun or fire a mortar at it.

Silver Key #15
You will find this key on the western edge of Mourningwood northward past the chest that is near a tree by the ruined wall. The key is within one of the arches on the wall.

Bowerstone Industrial
Silver Key #16
You will find this key inside the factory where the kids are working. This is just near the tunnel from Mourningwood. You will have to manipulate the levers to a particular order to turn off the steam vents in order to reach the key. The first lever you need to pull is up the stairs. Then pull the 2nd lever to the far right corner. The 3rd level you will need to pull is in the back left corner. Then finally pull the lever closest to the stairs that you climbed to have reached the balcony. You can now grab the silver key in the far right side of the room.

Silver Key #17
You will find this key when you become Ruler of Albion. Return to the military warehouse near the docks and climb the stairs to the upper level to reach an elevator car at the top that is now open. The key will be inside.

Bowerstone Market
Silver Key #18
You will find this key as you cross the bridge to the side of the river closest to the Millfields and head down the stairs to the river walk. It will be beyond the food stall near the sailboats at the end of the walkway.

Silver Key #19
You will find this key in the backyard of the Hauteville Heights house. Head down the path leading to the Bowerstone Castle exit and then enter the last house on the left side before the wall. Go through the house to reach the backyard.

Reaver’s Manor
Silver Key #20
You will find this key on Reaver’s bed in his private bedroom. To get to it, enter the bedrom to the right on the 2nd floor dinning room and then inspect the bookshelf which will reveal a secret hallway that leads to his private bedroom.

Bowerstone Castle
Silver Key #21
You will find this key as you make your way to the back of the gardens behind the castle. Go left at the steps that lead to the Catacombs and the key will be behind the statue.

Millfields
Silver Key #22
Find the Pepperpot Cave and follow the path beyond the fence to reach the large factory at the top of the hill. The key will be inside a small shack on the far side of the building.

Silver Key #23
Head to the mining factories and go past them and over the ridge towards the Bower Lake side of Millfields. Take the left path and go left right away again to see this key sitting out in the open.

Silver Key #24
Head down from the lake towards the mining area and keep going to the left towards the entrance to Dankwater Cavern. Head down to the pond below the cave entrance and swim over to the key on the left. It will also be directly below the statue with the telescope.

Bowerstone Old Quarter
Silver Key #25
You will find this key when you head through the rows of shops in the center of town and then turn left at the end. Climb the steps to where the path turns and purchase the Nightshade House on the right. It will be on the 2nd floor in this house you just purchased.

Silver Key #26
You will find this key during the quest “Battle for Albion” which is part of the storyline. It will be to the far left of the path leading up from the water in the corner of the area beneath the city wall.

Driftwood
Silver Key #27
Swim to the large island in the center of the 3 islands and find a small cave on the side of the island facing the main coast. You will find this key once you enter the small cave.

Silver Key #28
Climb up the outermost of the 3 large islands to the hobbe camp past the ledge where a chest is located. Leap off the plateau with the camp onto a ledge on the outer edge to find the key.

Shifting Sands
Silver Key #29
Find the large stone arch from Aurora at the end of Shifting Sands. Then look for a path that leads up to the dunes on the right. The key will be on this past before the arch.

Silver Key #30
Head to the large stone arch where Shadelight is and turn left. Follow the rocks here over the dunes and you will find the key.

Silver Key #31
You will find this key under the large slab of rock sticking out of the sand in front of the exit from Shadelight. Just cross the center of the dunes to reach it.

City of Aurora
Silver Key #32
While you make your way up the path that leads to the city’s gates, head past the Demon Door and the silver key will be in a small hollow to the right side.

Silver Key #33
Head down the looping path that is beneath the city gate, this will lead to a small rocky path near a large shrine. Then follow this path o the stone arch with hanging laundry and jump onto the lower roof. From here, keep jumping onto the lower rooftops to reach a low arch where the key is at.

Sandfall Palace
Silver Key #34
You will find this key in the far corner of the room containing the diamond. It will be to the left of the diamond in here.

Silver Key #35
Find the locked door on the left before reaching the first oasis. Then shoot the flit switch above the door 3 times to open the door. The key will be on a ledge behind this door.

Hideout
Silver Key #36
To get this key, open the door across from the jail cells on the middle floor of the Hideout. Head down the stairs to the lowermost level and then oen the cell around the corner to get to the key.

Silverpines
Silver Key #37
Head down the path southward to the small settlement and enter the Silverpines Mine. The key will be at the back of this cave.

Silver Key #38
Head down the main path towards the settlement in the center of the forest. Then take a left just before the settlement and follow this trail up the hill to find the key.

Cesspools
Silver Key #39
You will first need to dive off the ledge and afterwards head up the path and around the corner to the right. Then smash the wooden boards on the left side of the tunnel to grab this key.

Chillbreath Caverns
Silver Key #40
When you enter the cavern, find the rocky bridge and then follow the path across it to find the key. You may of grabbed this during the Missing Child quest.

The Ossuary
Silver Key #41
You will find this key in the open crypt near the entrance to the area from Mourningwood. It will be in the 4th crypt from the right.

Silver Key #42
First climb the stairs of the tomb near the entrance from Mourningwood. Then turn left at the first landing which is before the golden door. Then leap off the ledge here to land on the level containing the key.

Pepperpot Cave
Silver Key #43
You will find this key in the small pool of water at the far end of the cave.

Sunset House
Silver Key #44
To grab this key head up the path to the large clearing in Sunset House and then head around the perimeter up the hill to the mansion. The key will be amongst the rocks and trees on the right.

Silver Key #45
This key will be amongst the rocks to the left of the Demon Door.

Sewers
Silver Key #46
Find the sewer entrance that is beneath the crane in the far corner of Bowerstone Industrial. Then turn right at the first junction. The key will be around the corner near the metal bars.

Dankwater Cavern
Silver Key #47
After you complete the Hobnobbing with Hobbes quest, return to this cavern and enter the water via the slope where you left Dans Mourir. Then swim to the far left to the bank with the branching path leading out of the water. Then take the right path and follow it up to find the key.

Silver Key #48
After you complete the Hobnobbing with Hobbes quest, return to this cavern and enter the water near the hobbe camp. Then swim a counter-closewise spiral through the rocks and go right to work your way up the sloping path in the far left corner to grab the key.

The Veiled Path
Silver Key #49
Head to the far end of The Veiled Path and the key will be in the right corner at the top of the stairs.

Silver Key #50
Enter the area called The Enigma and shoot the flit switch to enter the 2nd room. Then light the 2nd brazier with the unwoven Fireball spell to open the nearby door. Go through the door to find the key at the top of the small circular platform.

found this info on www.videogamesblogger.com

This is the best and easiest guide on ALL Silver Keys