In case you haven't noticed, the pre-release of Minecraft 1.9 is out. The release includes

Listing of new features in the 1.9 prerelease. So far:

Nether specific:

• Nether blocks: Nether brick, Nether Fence, Nether Stairs http://i.imgur.com/lswAA.png
• Nether brick is flammable, it will stay on fire regular than a regular stone block but not indefinitely like Netherrack. Nether fences cannot be lit on fire.
• Nether Terrain Features: Strongholds & bridges of Nether brick (can be MASSIVE complexes) http://imgur.com/a/RUMiz
• Blazeman- Nether mob, A sort of Fire Elemental that comes from spawners and shoots fireballs http://i.imgur.com/U94ZX.jpg
• Magma Cube- Nether mob, look like a slime but upon jump they uncoil like a spring. They also will split apart into smaller versions of themselves when hit like slimes. http://imgur.com/a/xYgp9
• Nether items: Blaze Rod (dropped by new mob), Nether Wart (new crop) , Ghast Tear, Gold Nuggets (dropped by zombie pigmen)(put 9 of them together to craft into a gold bar)
• Farm-able Nether crop (Nether Warts), only plantable on soul sand.
• Ghast fireballs do not damage new Nether materials.
• Other than the gold nuggets, no uses for other new Nether items are known yet.

NPC Related:

• NPCs in villages, one main model with different colors for different "jobs." Pics here: http://www.reddit.com/r/Minecraft/comments/knx1o/minecraft_19_pre_out/c2lrg2m
• NPCs will not react to attacks on other NPCs
• Hostile mobs will not go after NPCs, but can kill them while coming after you.
• NPCs do not have any specific purpose of actions yet, they kinda just walk around.
• NPCs will only appear in towns newly generated in 1.9; if you have villages generated in any stage of 1.8 there will be no NPCs

Other features:

• Swamps: darker colored water and lily pads http://imgur.com/tRSB4.png http://mc.jarryd.net/prettynewswamps.png
• The shade of the water seems to depend on the biome the water is located in: If you pour "swamp water" into a non-swamp biome, you get normal-shade water. If said water flows from a non-swamp biome into a swamp biome, it changes colour at the biome border.
• Red flowers and Snow Biomes are back!
• Mushroom Biome! purple tinted grass and large mushrooms growing. http://ii.snag.gy/zwfpr.jpg
• "Mooshroom" cows appear in Mushroom biome, can be sheared to get mushrooms and then turn into regular cows http://imgur.com/NNi99
• Snow "Golem"- can be crafted by placing two snow blocks vertically on the ground, and then placing a pumpkin head on top of them. NOTE: They are crafted by block placement not a crafting square! http://i.imgur.com/Vx4OW.jpg http://mc.jarryd.net/littlebabbysnowman.png
• Rain is re-textured.
• Water and Lava leak through adjacent blocks. http://i.imgur.com/KQL09.png
• Chests now make no sound at all.
• Holding space no longer allows sustained jumping; must tap jump key for each jump.
• When flowing lava falls on top of water, smoothstone is created. When flowing water hits flowing lava, cobblestone is created

Bug Related:

• FIXED- Stair lighting issues Except with smoothstone stairs
• Experience bar changes every time the player jumps (Jeb tweeted that it's not a bug, it "is to test SMP exp orbs... "
• Swamp water and regular water appearing side by side for bad visuals. http://imgur.com/tRSB4.png (left side)
• Reports of a lot of players having major FPS problems. Lag spikes of death are not yet defeated
• Bow sometimes has extra-long melee range?
• Swamp Grass blocks have improper grass coloring on their sides.
• Shearing "Mooshroom" cows gives the "getting wood" achievement
• Shift clicking items when you craft doesn't get tracked in your stats properly
• Preexisting light sources (lave, flaming netherrack, etc) might not give off light properly.

    b[mn.v.bG] = true; // grass
    b[mn.w.bG] = true; // dirt
    b[mn.F.bG] = true; // sand
    b[mn.G.bG] = true; // gravel
    b[mn.ae.bG] = true; // flower
    b[mn.af.bG] = true; // rose
    b[mn.ag.bG] = true; // mushroom
    b[mn.ah.bG] = true; // mushroom
    b[mn.an.bG] = true; // TNT
    b[mn.aW.bG] = true; // cactus
    b[mn.aX.bG] = true; // clay
    b[mn.bb.bG] = true; // pumpkin
    b[mn.bs.bG] = true; // melon
    b[mn.bz.bG] = true; // mycel

Full version of Minecraft.[2] Updates will continue to be released after it.[3]

Fixes & Changes:

New achievements
Will limit the amount of Experience Orbs dropped by a player on death.[4][5]
The ability of Endermen to carry blocks will be reduced in some way.[6]
New Monster Spawner texture.
Ghast fireballs have a different texture.
On death, a proper score is given based on how many experience orbs the player has collected.[7]
When flowing lava hits a water source directly from above, it creates Stone where previously the lava would flow through the water.
You can toggle between three states when pressing F5 (first person, third person back, third person front), having the addition of 3rd person view from the front.[8]
Ender Pearls will have a unique ability.[9] When thrown, the player will teleport to the Ender Pearl's impact location, but take 2 and 1/2 hearts of fall damage. They will not work in Creative.[10]
Golden Apples now glow purple in inventory.
Fences no longer block you from moving onto their space. You can now stand next to them, like you can with glass panes and iron bars.
They will also connect to solid blocks.[11]
There is a slight delay between jumps when holding down the jump button, so that the player no longer bounces between ceiling and floor in two-block-high spaces.
Labels for items will be changed.
Random loot chests in Strongholds.
Blocking now moves the player's arm, rather than the sword just floating right in front of the player.
Weapon and tool damage has been nerfed to make space for the increased damage enchantments, (Diamond swords do 3.5 hearts now instead of 5)
Some mob health has been changed (Sheep, Spiders, Zombies)

New Features:

This update will include new features in the Nether, such as:
Nether Bricks.[12]
Nether Fence.[13]
Nether Stairs
Nether fortresses.[13]
This update will also include "The End" (unofficially called "The Ender", or "Enderlands"), which replaces the previously announced Sky Dimension.
End Portals takes the player from the Overworld to The End. To go back to the Overworld, one must jump in the End's void.
End Portal Frame (Name not confirmed)
End Portal Block (Name not confirmed)
End Stone
New Items:
Ghast Tear
Blaze Rod
Nether Wart
Gold Nugget
Glass Bottle
Spider Eye
Fermented Spider Eye
Blaze Powder
Magma Cream
Glistering Melon
Eye of Ender
Activates Ender Portal Frame blocks.
9 new Music Discs.
Finished Biome code and New Biomes.[14]
Snowy Biomes.[15]
Swamp Biomes will be adjusted to appear "swampier."[16]
Darker Grass
Darker Water
Lily Pads
Mushroom Biomes.[17]
Naturally generated Huge Mushrooms.
New Mushroom Cow, the Mooshroom.[17]
Mycelium blocks.[17]
New sound effects,[citation needed] including:
Minecart sounds.
Shears sounds.
Additional Bow sounds.
Big Slime sounds.
The true sounds of Endermen and Silverfish.[18]
Changes in already existing sounds:[citation needed]
A change in the sound of Rain.
New sounds for Doors.
New sounds for the Skeletons' walk to make them sound more skeleton-y.
Bow models now appear in third-person larger and in 3D.
If water or lava is above a ceiling that is a single block thick, particles of water or lava will drip through, provided you are within 13 blocks of the ceiling.[19]
6 New Mobs:
Enderdragon (Boss Mob)[20][21]
Enderdragon eggs[22]
Mooshroom Cows.[23][24]
NPCs in Villages,[25] as Villager Mobs.[26]As of 1.9pre5, they are basic, but they will soon have more AI.[27]
Snow Golem mob.[28][29]
Can be crafted.[30]
Melts in hot biomes.[30]
Spreads snow around when it walks.[31]
Passive, but throws snowballs at enemies.[30]
At least two new aggressive mobs for the Nether.[32][32]
Magma Cube
Blaze
Use for Experience (skills) will be added.[33]
Each Experience Orb is worth one Score Point.[34][35]
Animal Breeding.[36][37][38]
Wheat Bundles feed animals and make them come towards you.[39]
Feeding animals makes them enter "love mode".[40]
Hearts will come out of animals while in love mode.[41]
Breeding will produce Baby Animals.[42] Smaller versions of the parents with large heads that have a faster animation and a higher pitched sound.
Increased number of Strongholds per map (from three to unlimited).[43]
New/Improved Armor system.[44][45]
Increased armor durability.[45]
Sun and moon changes:
Moon phases.[46]
Sun and moon now rise in the east.[47]
Sun and moon are now round.[48]
Game mechanics changes:
Hardcore Mode - Locks the difficulty to Hard and forces you to delete your world if you die. The health bar changes appearance to indicate you are playing in Hardcore mode.[49]
Item Repair[50][51]
Potions, Splash Potions, Potion effects, Brewing Stand, and Brewing.[52][53][54][55][56]
Enchantment Table, and Enchanting[57][58]