These are all that I've found so far.

North Redmoon:

Manu: (213, 292) and (237, 313)

Glacmore:
(335, 137)
Glacmore skills academy: (inside it. these are coords for the area. you do not have to be in these exact spots for this to work.)

Crafting- 258, 272
Potions- 256, 210
Fast Reading- 303, 315
Alchemy- 293, 274
(now there may be more double xp places in the academy. However I did not find them while going around making helms, potions, fe and thread.)

Desert Pines:

Fast Reading Room: 280, 115. "Use" the coin in the boulder.

Alchemy- 28, 199
Alchemy- 189, 284
Alchemy- mm 323, 143

White Stone:

Alchemy- Elavro Mountains 705, 568
Crafting- Orvale Mountains 48, 360
Manufactoring- Lakeside Village 564, 123

Morcaven March:

Potions- 187, 162
Alchmey- 323, 144

Narlik:

Magic- 154, 177 *Note* I went there and cast spells however. they cast and actually worked. And I did not receive double xp. However the place does "welcome" you to a magic school.

Portland:

manu: (96, 105)
Potions: (274, 267)

Willowvine:

Skills acedmy and storage: (176, 121) on the bridge.
*school area's in the school building.*
manu: (304, 312)
summoning (271, 305)