Note: Very few references are provided here because all of this content has been directly released in weekly snapshots 12w03a to 12w08a.
As of snapshot 12w03a:
- Ladders regained their collision box.
- Vines are climbable if you push into a solid block while next to them.
- Added jungle biomes (requires a new world or new chunks) with ferns and new wood and leaf types.
- Updated language files.
- Dispensers dispensing Spawn Eggs will place Mobs instead of simply dispensing the eggs.
- Spawn eggs are now stackable.
- Zombies have new path-finding AI.
- Wolves have new AI and can be bred using Raw Chicken, Cooked Chicken, Raw Porkchops, Cooked Porkchops, Raw Beef, Steak, or Rotten Flesh, when tamed.
- New jungle-specific Ocelot mob that can be tamed into Cats using Raw Fish.
- Mobs in general have new a AI with new and improved behaviors.
- New Items:
- Updated Language files.
- Changed Dispenser and Oak Sapling textures. ()
- Added Desert Wells.
- Players are slowed when going through Vines due to their nature of being a collision-less Ladders.
- New Mob behaviors.
- Creepers run away from Cats and also stalk players.
- Cats can be told to sit.
- Mobs no longer attempt to jump over Nether Brick Fences.
- Creepers run away from Cats and also stalk players.
- Villagers will try to detect village houses and live in them.
- Lava now has sounds.
- Ocelots are easier to tame.
- Abandoned Mine Shafts now bridge over gaps in paths.
- Enchantment Tables no longer require Experience in Creative Mode.
- Updated Language files, having "50%" less profanities.
- Redstone-related items can be placed on Glowstone Blocks again.
- You can get Dead Bushes by using shears on them.
- Fixed shift-clicking the result from Crafting only giving one item regardless of the amount of material used.
- Cats will now sit if right-clicked with an empty hand.
- Death screen has a slight delay before buttons become active, to avoid accidentally clicking buttons when killed.
- Survival MultiPlayer mob hitboxes are fixed, so they apply to the full mob, instead of only the head.[1]
- Many minor bug fixes and tweaks.
- Doors have been changed to properly detect if they are open or closed. Double Doors in existing maps will need to be updated.
- Placing two Pressure Plates directly in front of doors and stepping on them will open them correctly.
- When stepping on a single Pressure Plate only the door on that side will open.
- When stepping on both Pressure Plates both doors will open.
- When stepping on a single Pressure Plate only the door on that side will open.
- Placing two Pressure Plates directly in front of doors and stepping on them will open them correctly.
- Villager's AI has been improved.
- When a player aggros a hostile mob, it will continue to track the player despite being attacked by other mobs.
- Zombie's AI has been improved.
- On Hard difficulty and Hardcore Mode, zombies break down Doors.
- On normal and easy Difficulty, zombies attack but will not break down Doors.
- Zombies chase and attack Villagers.
- Zombies attack doors when attempting to escape sunlight.
- On Hard difficulty and Hardcore Mode, zombies break down Doors.
- Added new sounds.
- Better movement for mobs in Water.
- Mobs move slower.
- Added rare Item drops for mobs.
- Zombies have a rare chance to drop a Iron Ingot, Iron Helmet, Iron Shovel, or an Iron Sword.
- Skeletons have a rare chance to drop a Bow or an Enchanted Bow.
- Zombie Pigmen have a rare chance to drop a Golden Helmet, Gold Ingot, Golden Sword, or an Enchanted Golden Sword.
- Zombies have a rare chance to drop a Iron Ingot, Iron Helmet, Iron Shovel, or an Iron Sword.
- Pressing F1 disables hitbox outlines on blocks.
- Monster Spawners now show correct mobs in multiplayer.
- Snow Golems take damage from rain and water.
- World format changed for the second time, conned "Anvil", with an automatic world converter from the current "McRegion"[3].
- Maximum build height increased to 256 (was 128).
- Empty sections of the world will not be loaded into memory.
- Block ids increased to 4096 (is 256) by adding a 4 bit data layer (as of this snapshot it is only working for items).
- Block ordering will be changed from x/z/y to y/z/x in order to improve compression.
- Packets for sending chunks will be updated (a full 128-high chunk is smaller than the old format, and a chunk with lots of empty space is much smaller).
- Biomes will be saved per x/z column, which means they can be altered by tools.
- Maximum build height increased to 256 (was 128).
- Light calculations in SMP take place client-side
- Remaining animals were moved into new AI system.[4]
- Added Redstone Lamp [5]
- Decreased dropping chance for rare items
- Villagers repopulate villages based on the number of houses
- Zombies have a chance of attacking villages at night (part of the upcoming Sieges feature)
- Villagers have children, which always sprint
- Added Iron Golem, a new utility mob.
- Added upside-down stairs.[8]
- Many changes to the world and lighting system.
- Sieges between zombies and villagers.[9]
- Support for folder-based texture packs.[10]
- Upside-down half slabs.[11][12]
source: http://www.minecraft...coming_features