This guide is a simplified overview of all the changes in the Horse Update (Java Edition 1.6.x releases), which assumes at least some familiarity with the Redstone Update (Java Edition 1.5.x releases).
Mobs [ ]
New [ ]
Name
Image
Habitat
Drops
Note
Horse
Spawns in plains
Creation assisted & inspired by DrZhark's Mo' Creatures mod
To tame, ride them and get thrown off a few times until hearts appear
Can be bred using Golden Apples & Golden Carrots
Health can be restored using Bread, Sugar, Hay Bales, Wheat, Apples, Golden Apples & Golden Carrots
Baby Horses can be grown the same way
Players riding saddled Horses are granted full control over the Horse's movement
Color, style, maximum health, jump height and speed vary between Horses
Open your inventory, right click a Horse or press the inventory key while holding LSHIFT and looking at a Horse to access their inventory to deal with their storage, armor and saddle
Rarely spawn in small groups
Donkey
Spawns in plains
Like horses, but smaller and gray
Can carry chests with 15 slots on their saddles
Mule
Only spawns by breeding a horse with a donkey
Can wear chests on their saddles, just like donkeys
Not breedable with horses, donkeys, or other mules
Skeleton Horse and Zombie Horse
Can be spawned only by using third party programs.
Introduced as the code of the normal Horse, although require third-party modifications to be used in the game.
Aren't used at this time
Changed [ ]
Name
Image
Changed
All mobs
Mobs named "Dinnerbone" or "Grumm" are now flipped upside down.
Now spawn in groups again.
Zombies
Now have a small chance to spawn additional zombies when damaged or not being looked at.
Able to lock onto the player from 40 blocks away (formerly 16 blocks).
Zombies that are locking onto a player can now move when further than 32 blocks away.
Withers
Armor has been retextured.
Blocks [ ]
New [ ]
Name
Image
Obtaining
Tool Required
Uses
Hardened Clay
Pickaxe
Stained Clay
Pickaxe
Can be used as a decorative block
Carpets
Any
Can be used as a decorative block.
Hay Bale
Any
Can be used as a building block.
Can be used as compact wheat storage.
Can be used to accelerate the growth of horses.
Block of Coal
Crafted only with coal, not charcoal.
Pickaxe
Can be used as a building block.
Can be used as compact coal storage.
Can be used as furnace fuel to smelt 80 items, which is more than its individual 9 coal ingredients can (72 smelted items).
Changed [ ]
Name
Image
Changed
Lapis Lazuli Block
Retextured subtly, it now has a border around it
Redstone Comparator
Now gives a redstone signal for Cauldrons and End Portal frames depending on their state
Cauldrons give a signal strength of zero (empty) to three (full), depending on the water level
End Portal frames give a signal strength of either zero or fifteen, depending on if an Eye of Ender has been inserted
Items [ ]
New [ ]
Name
Image
Obtaining
Uses
Horse Armor
Cannot be crafted and it can only be found in most types of generated chests, including in Dungeons, Nether Fortresses, Desert Temples, and Jungle Temples
Lead
Can be used to bind mobs to fences or lead them around
Right click mob first, then right-click fence or right-click the mob again to get the leash back
Name Tag
Found in dungeon chests
Name it in an anvil, then right click a mob to name it.
Horse Spawn Egg
Can be obtained via Creative inventory.
Works like any other spawn egg
Sometimes a Donkey will be spawned instead
Changed [ ]
Name
Image
Changed
Charcoal
Retextured, with more brown shading to differentiate from coal
Saddle
The player can now put a saddle on a horse
Golden Apple
Golden apples now require gold ingots instead of gold nuggets to craft
Golden apples now give Regeneration II for 10 seconds and both tiers give Absorption for 1 min 30 seconds
Glistering Melon
Glistering melons now require 8 gold nuggets
Biomes [ ]
Changed [ ]
Name
Image
Changed
Deserts
No longer contain water lakes.
Effects [ ]
New [ ]
Name
Image
Causes
Description
Absorption
Golden Apples
Increases damage absorption.
Health Boost
Golden Apples
Increases maximum health.
Saturation
Food
Decreases hunger loss.