GW2DB

Bone Shards can be commonly farmed from the Grawl mobs in Diessa Plateau. For an exact location (Sanctum Waypoint) check out my video; Grawl Small Totem & Bone Shard Farming Guide.

Note: The Grawl also drop Small Totems which sell for just a little bit more than Bone Shards do.

Instead of directly farming these another great way to get them is by opening the "Moldy Bags" in the game. These have an extremely good chance of giving you a fine crafting material (a blue one, like this one) and are rather cheap on the Trading Post. Usually ranging from 20 - 50c a bag, depending on the type of bag.

While you won't get rich buying bags, opening them and selling the reagents on the Trading Post you definitely will be able to stock up your collectibles tab at an insanely fast rate. I made a video on how this method works, if you'd like to see it: Fine Crafting Material Farming Video for all skill ranges.

Here are a list of all the bags in the game so you know which type you'll need to buy for whatever item you're after.

Tiny Moldy Bags (0 - 50 Components)

Small Moldy Bags (25 - 100 Components)

Light Moldy Bags (75 - 175 Components)

Moldy Sacks (150 - 250 Components)

Medium Moldy Bags (175 - 300 Components)

Large Moldy Bags (300 - 325 Components)

Heavy Moldy Bags (325 - 400 Components)

Snowden Drifts, North West at Skradden Slopes, South of Skradden Waypoint there is a skill point in a cave, Grawl in the cave drop these often actually, they around lvl 23-24 and they spawn fast they also drop a small totem now and then but the bone shards are the higher drop, i think using a magic find bonus food buff will help you too though I cant be 100% sure on that. Also going north you find more sons of svanir and they drop small totems but its like 1 out of every 8 you kill, as said here they are rare. 

go find the Skritts at mining site, at the north of the Lornar's Pass. they drop bone shards and small scales

I am farming these off of grawl in Diessa Plateau. Near the sanctum waypoint. They also drop the small totems. Just outside the cave are hyenas for small claws, and forest spiders for small venom sacs.

I can confirm they have a decent drop rate, and they respawn really quickly. Small totems are rare, though.

Nice drop rate from Skritts near Icedevil's Waypoint in Lornar's Pass, especially during the nearby event @ Skritt Hill. Without plugging the holes with boulders you can plunder the Skritts and pick up a nice stack of these bone shards.

Farmed the skritt there for a bit with a friend - got only one shard in 40+ kills between us. That's 40+ kills with 2 players looting so 80+ loot chances (one loot chance for each player per mob). Either a very bad tip or extremely unreliable droprate. I did get 2x Small Scale[s] though, and a stack of Crumbling Bones.

Cave trolls in 3rd norn area....

3rd? you mean the first one that's 25-40 and the story quest goes there?

And where are they?

Does anyone know any good locations where to farm these? and other crafting ingredients? Thanks!