Here’s an oddity for those who have tailors with Northrend Cloth Gathering. From 85 up, farming the trash mobs in Icecrown for Frostweave Cloth grants more XP than the same Cataclysm mobs in Deepholm for Embersilk Cloth, slightly more than double. At 88 on my tailoring/enchanting mage last night, I was averaging about 1,100 XP per kill in Icecrown, but only 450-475 XP per kill in Deepholm.
Unless you have an alchemist that can make Potions of Treasure Finding super cheap for you, you’ll also probably net more gold from Icecrown farming as well; Wrath items disenchant to infinite dust, which seems harder to come by on my server’s AH. (Your mileage and markets will vary)
If you’ve got a toon slowly working to 90, consider sending them out to Icecrown after you check your AH prices. You’ll have an easier time grinding, get double the XP, and make some coin in the process.