Level 35 and 200 required:
The Leatherworking specializations are now re-trainable, for a fee.
Tribal is now more related to Druids/Shammys. (Spell-Crit Bonuses)
Dragonscale is now related to Hunters/Shammys. (It is still mail-gear, spell crit.)
Elemental is now related to Rogues/Hunters. (Bonus to Crit/Agi)
Everything can of course can be used by the other leatherwearing classes, but this is the classes that will want to focus on said types.
The most important part of the changes is that ALL types of leatherworking can be learned by a non-spec leatherworker of the appropriate skill level. However, you will have to specialize to make certain Blue and Epic patterns, some of which will be BoP only now. So specialization still exists, but it has changed as to what classes it would be most useful for, slightly.
You will want to check with -all- of the types of trainers, starting with your highest normal LWing trainer, and moving on to the specialization trainers. There are patterns one can use that you could not previously. (Green Dragonscale Gauntlets for example, from Dragonscale).
Tribal LW Trainer is found at the Thalanarr FP. (She stands near the edge of Thousand Needles and a gazebo.)
Dragonscale LW Trainer is found in Azshara near Forlorn rock to the right. (From the FP, around the rock on the right, a small tent near him)
Elemental LW Trainer is found in Searing Gorge, near Grimsilt's Dig Site. (Enter from the Badlands, directly to your left past said site, a small tent near her.)
Some of the drop patterns are now open to created by any leatherworker, but be cautious, some of these will also now be BoP. Some of these are Blue and Epic gear to be created, non-BoP.