The following areas have been given atleast a 20% hike in exp. Please remember that a mobs age greatly effects a mobs xp, as does a player's kill history...
draconian sewers
Graveyard
Penguin Vale
Kingdom of Jrontauq
Kendermore
Dalina Mansion
City of Theris
River of Blood
The Town of Drexel
Ettin Village
Valley of the Mage
Dungeons of Kara'sa
M.A.G.I.C
Tower of Nexialism
L.A.A.A.A.M
Castle Roogna
Forsaken Swamp
City of the Undead
Castle of Perseverance
Lycanthropia
Ming's Temple
Ch'ung Kuo
Undead Burial Grounds
The Labyrinth
The Infirmary of Farlorne
The DemonWeb and Citadel
Kuo-Toan Hamlet
Palace of Thalassas
The Mines of Moria
Sky Elves
The Sahaguins
Enjoy,
Splork