Silver Keys can be found in various places in all Albion. Mostly you'll have to fish or dig them out. They are often hidden in water, in places indicated by recognizable bubbles, or below the ground level, in flowery circles. In other cases you just have to stick your nose practically everywhere.
The only purpose the Keys have is to open Silver Key Chests. Each one of them has a number on it - it indicates the number of keys required to open it. The keys don't 'disappear' after use, so when you have 20 keys in your inventory, you can open all the chests that require less than 21 of them. The Chests contain some of the most valuable items in the game (including legendary weapons, special armors and some neat potions), so be sure to check them out.
1. Lookout Point
You'll find a bush that can be cut in the center of the area. The key is right behind it.
2. Bowerstone South
Enter the tailor's shop and go upstairs, the key is on the balcony.
3. Greatwood Lake
It's right near the broken bridge.
4. Fisher Creek
Fish it from one of the bubble-points on the lake.
5. Orchard Farm
Fish it from the pier in the eastern part of the map.
6. Guild Woods
You'll have to fish again, this time it's in the lake nearby the Guild.
7. Darkwood Lake
Use the bow to hit the opening in the mysterious stone in the middle of the area, and the key will be yours.
8. Ancient Cullis Gate
Use your fishing rod on the bridge in the western part of the map.
9. Grey House
Fish it out near the Demon Door.
10. Memorial Garden (Oakvale)
You'll find this key while doing the Treasure of the Ghost Pirate Quest. It is buried near the axe-wielding statue.
You can win this one in Chicken Kicking Competition (you score has to be between 150 and 250 pts.)
12. Rose Cottage
Dig in the flower circle near the cottage.
13. Hobbe Cave
Dig in the mushroom circle in the large room where you find the missing boy in Hobbe Cave quest.
14. Twinblade's Camp
Dig in the flower circle in south-western part of the area.
15. Witchwood Stones
Fish it out near the Demon Door.
16. Witchwood Lake
Dig next to the red-glowing statue.
17. Knothole Glade
Use your shovel in the plant circle between two houses in the southern part of the town.
18. Windmill Hill
Dig it out from the circle of flowers next to the cottage.
19. Windmill Hill
The same thing as with key #18, except the circle is near the windmill this time.
20. Headman's Hill
Fish it out from the pond you fall into while fighting Thunder (you must be doing the Lady Gray quest).
21. Bowerstone Manor
Examine Lady Gray's bed (doh).
22. Lychfield Graveyard
Dig it out from one of the graves in western part of the map.
23. Lychfield Graveyard
It's in the sarcophagus in one of the crypts.
24. Lychfield Graveyard
Fish it out from the muddy pond in the center of the map.
25. Cliffside Path
It's buried in the circle of red mushrooms on the northern edge of the map.
26. Hook Coast
Examine the cabinet inside the lighthouse (you have to slam the door).
27. Fisher Creek
You can win it in Fishing Competition (look in the bronze quests' section).
28. Bowerstone South
Just donate 25 books to the school in the Book Collection quest.
29. The Lost Bay
Dig it out of the grave near the 30-key chest.
30. The Necropolis
Use your fishing rod in the river, near the broken bridge.