Leatherworking

Allakhazam's Leatherworking page is here, and Thottbott's is here. Thottbot's is a little better, IMO, but if you're interested in drop- or vendor-only patterns, Allakhazam's page lists these on their page, just click the <Pattern:X> link under the name of the item on the list above to see where to get it.

For Alliance, the Artisan Leatherworker is in Darnassus, and the Master Leatherworker is in Aerie Peak.

For Horde, the Artisan Leatherworker is in Thunder Bluff, and the Master Leatherworker is in Camp Mojache.

After level 40, and when your leatherworking skill is sufficiently high (Artisan is required), you can specialize in one of the 3 branches of leatherworking:

Tribal Leatherworking quest The Horde Tribal Leatherworker is south of Grom'gol. The Alliance Tribal Leatherworker is in Thalanaar, on the east side of Feralas, next to the Alliance flight point there.

   Trained
   * Wolfshead Helm - 109 AC, 10 Spi, When shapeshifting into Cat form the Druid gains 20 energy, when shapeshifting into Bear form the Druid gains 5 rage. (Lvl 40)
   * Feathered Beastplate - 146 AC, 10 Int, 24 Spi (Lvl 45)

   Chimeric
   * Gloves - 87 AC, 11 ArcaneRes, 12 NatureRes (Lvl 48)
   * Boots - 99 AC, 12 ArcaneRes, 12 NatureRes (Lvl 50)
   * Leggings - 127 AC, 16 ArcaneRes, 16 NatureRes (Lvl 51)
   * Vest - 150 AC, 16 ArcaneRes, 17 NatureRes (Lvl 53)

   Ironfeather (set bonus: Increasts your resistance to slience by 5%.)
   * Shoulders - 117 AC, 20 Int, 8 Spi (Lvl 49)
   * Breastplate - 165 AC, 12 Int, 28 Spi (Lvl 53)

   Warbear
   * Harness - 158 AC, 11 Str, 27 Sta (Lvl 50)
   * Woolies - 142 AC, 28 Str, 12 Sta (Lvl 52)

   Frostsaber
   * Boots - 99 AC, 12 FrostRes, 12 ShadowRes (Lvl 50)
   * Leggings - 129 AC, 17 FrostRes, 16 ShadowRes (Lvl 52)
   * Gloves - 95 AC, 13 FrostRes, 12 ShadowRes (Lvl 54)
   * Tunic - 158 AC, 18 FrostRes, 18 ShadowRes, (Lvl 57)

   Devilsaur (set bonus: Improves your chance to hit by 2%.)
   * Gauntlets - 103 AC, 9 Sta, +28 Atk, +1% crits (Lvl 53)
   * Leggings - 148 AC, 12 Sta, +46 Atk, +1% crits (Lvl 55)

Elemental Leatherworking quest There is an Elemental Leatherworker west of Thoradin's Wall, on the Arathi side. (Horde or Alliance?)

   Trained
   * Gauntlets of the Sea - 85 AC, 7 Agi, Heal friendly target for 300 to 500. (Lvl 41)
   * Helm of Fire - 118 AC, 17 Agi, 10 Sta, 5 FR, Hurls a fiery ball that causes 286 to 376 Fire damage and an additional 40 damage over 8 sec. (Lvl 45)

   Living
   * Shoulders - 117 AC, 13 Spi, 8 NatureRes, Increases healing done by spells and effect by up to 28. (Lvl 49)
   * Leggings - 142 AC, 25 Spi, 8 NatureRes, Increases healing done by spells and effect by up to 24. (Lvl 52)

   Stormshroud (set bonus: 5% chance of dealing 15 to 25 Lightning damage on a successful melee attack.)
   * Pants - 138 AC, +2% crits, +1% dodge (Lvl 50)
   * Armor - 163 AC, +2% crits, +1% dodge (Lvl 52)
   * Shoulders - 114 AC, 10 Sta, +1% crits, +1% dodge (Lvl 54)

   Volcanic (set bonus: 5% chance of dealing 15 to 25 Fire damage on a successful melee attack.)
   * Leggings - 204 AC, 20 FireRes (Lvl 49)
   * Breastplate - 268 AC, 20 FireRes (Lvl 52)
   * Shoulders - 167 AC, 18 FireRes (Lvl 56)

Dragonscale Leatherworking quest There is an Alliance Dragonscale Leatherworker in Azshara; from the entry point at the west side, roughly to the east and south of the naga-inhabited ruins.

   Trained
   * Dragonscale Breastplate - 306 AC, 10 Sta, 13 FireRes, 13 FrostRes, 12 ShadowRes, Absorbs 600 magical damage (2 minutes) (Lvl 46)
   * Dragonscale Gauntlets - 171 AC, 7 Sta, 6 Spi, +1% crits (Lvl 40)

   Green Dragonscale
   * Breastplate - 311 AC, 25 Spi, 11 NatureRes (Lvl 47)
   * Leggings - 282 AC, 26 Spi, 11 NatureRes (Lvl 49)

   Blue Dragonscale
   * Shoulders - 338 AC, 28 Int, 8 Spi, 8 AR (Lvl 52)
   * Breastplate - 262 AC, 21 Int, 6 Spi, 6 AR (Lvl 54)

   Black Dragonscale
   * Breastplate - 344 AC, 8 Sta, 12 FireRes, 50 Atk (Lvl 53)
   * Shoulders - 266 AC, 9 Sta, 6 FireRes, 40 Atk (Lvl 55)
   * Leggings - 320 AC, 8 Sta, 13 FireRes, 54 Atk (Lvl 57)

   Red Dragonscale
   * Breastplate - 360 AC, 12 FireRes, Increases healing done by spells and effects by up to 60. (Lvl 56)