OK, been kinda following what the changes are for this next 1.3 MineCraft release and since it's only 2 days until the release I thought I'd post what I believe are the most exciting changes I've discovered via looking at the snapshots and pre-release.
Firstly, Emeralds, Trading and Ender Chests:
Emeralds ... a few key facts to remember are:
They only generate in Extreme Hills Biomes, between the Y Coordinates layers of 31 down to 4. Their occurrence is about 8 times per chunk and they only generate in veins of 1 ore at a time. Apparently this makes them 25 times rarer than diamonds!
Emeralds can be traded with villagers or turned into building blocks much the same way as Lapis, by filling the 9 spaces of the crafting table with emeralds will create one block.
Trading With Villagers!
You can do 3 types of trades with villagers. They will either give you emeralds in return for items, give you items in return for emeralds or enchant a tool for you in return for emeralds.
When you do a trade with a villager, there is a chance that he will offer another type of trade as well as offering the previous trade as well.
The five different classes of villagers trade in different materials.
Farmers Trade in:
Apples, Melons, Wheat, Bread, Cooked Chickens, Cookies and Flint & Steel.
Butchers Trade in:
Any leather armour, Any Food and Coal.
Blacksmiths Trade in:
Coal, Iron Ingot, Gold Ingot, Any Tools and Any Armour.
Librarians Trade in:
Paper, Books, Bookshelves, Paper, Compass's and Glass.
Priests Trade in:
Bottle o Enchanting's, Eyes of Ender, Glowstone, Redstone and ... Rotten Flesh?
Apparently, villagers remember if you attack them, raid their chests, steal from them or destroy parts of their village... in turn, they will offer very bad trade options to you.
Villager Spawner Eggs will now spawn a random villager profession.
I actually found this video summed up most of what I found via Google.http://www.youtube.com/watch?v=ivUj5cAxnhA
1 Eye of Ender surrounded by 8 pieces of Obsidian = 1 Ender chest with 27 slots.
Basic idea of this chest is that you make an Ender Chest, place items inside, travel half way across the world or even to the Nether/End World and make another Ender Chest and Voilà!! You have access to the items you placed in the first Ender Chest ... and you can make as many of these chests wherever you like and it will act as an access point to the same 27 slots wherever you are.
Few things to note are:
You can destroy an Ender Chest with any type of pickaxe. However unless you use a Silk Touch Pickaxe, it will drop 8 pieces of obsidian instead of an Ender Chest.
Due to the fact that they are made of Obsidian, they have the same blast value as Obsidian ... immune to TNT and Creepers ...
apparently not immune to the Ender Dragon blast though.
You can not double up an Ender Chest to make a double Ender Chest with 54 slots like a normal chest. It is just a single Ender Chest with 26 slots.
Finally, all the hype about the Ender Chest inventory being shared with every player in multiplayer ... well, that's changed.. as of 12w24a the Ender Chests are now player specific so what you place in your Ender Chest should not be accessible by other players.
Other Awesome Changes:
You can now get Experience from mining ores as well as from killing mobs, the higher the ore the more XP you will get ... for example, mining a Diamond Ore gives you more XP than mining a Coal Ore. You can also get a little XP via smelting in a furnace.
The maximum Enchantment Level has been changed from 50 down to 30. However, the 3'rd enchant slot show the max level more often and you get a much higher chance of getting multiple enchantments on the one tool at the highest level.
However due to these changes, the XP needed to go up a level has raised slightly.
Enchanted weapons, armour and tools now glow for other players too. So you can see if somebody has something enchanted equipped!
You can now shift click for Enchanting Tables, Brewing Stands and Equipping Armour.
Wooden Logs can now be placed at three different directions, such as sideways. You place them directionally much the same way as you place pistons directionally.
Any wooden slabs crafted from update will act like wood, not stone.
All 4 types of wooden slabs included. All 4 types of Wooden Stairs included.
Also Sandstone Stairs added... YAAAY! Wooden and Sandstone Stairs!
Oh and slabs and stairs can now be placed upside-down!
You can now make Books & Quill with up to 50 pages!
Though, the crafting recipe for a Book now = 3 paper and 1 leather (In any pattern)
The crafting recipe for a Book & Quill = 1 ink sac, 1 feather and 1 book (In any pattern)
If you drop multiple stackable items on the ground they become one item stack like in your inventory.
So basically that means if you drop 64 melons on the ground, instead of there being 64 floating melons everywhere, there just shows as 1 melon on the ground and when you pick that up you have picked up all 64 melons.
Drowning .. you know when you've run out of air and you're drowning but you're only 2 blocks from the surface but the drowning keeps knocking you back down into the water?
Well .. not anymore ... drowning doesn't do knockback damage anymore so now you have a chance of saving yourself while drowning.
You can now make Tripwires!
To make a Tripwire you first need two Tripwire Hooks and some string.
To craft the TripWire Hooks on the crafting table you place an Iron Ingot on-top of a Stick on-top of a Wooden Plank ... makes two Tripwire Hooks.
You then place these two Hooks opposite each other, up to 40 blocks apart and then place String on the ground between the two in a STRAIGHT line. Then when a mob or player walks between the two hooks, it will set up the TripWire Hooks the same way as any other switch!
To break the trap without setting off the switch you must use shears on the string.
This also allows you to place string as a decorative block.
Oohh.. Errr... on the GON MineCraft Server ... for this to work we may need to disable the right click option on string that shows the RG Info? We have /RG INFO Command anyway?
Using lava buckets as furnace fuel will return an empty bucket.
Empty buckets will stack up to 16 Buckets now.
Cocoa beans - can be obtained by destroying a jungle tree .. 1/200 chance of getting a bean. Or, you can plant them on jungle trees to grow them.
Nether warts can be grown in the Overworld now but you must plant them on soul sand still.
Boats don't get destroyed by Lilypads anymore and if you break a boat it drops the boat as a resource now.
Pistons take 0.05 seconds longer to extend.
Not sure how this will affect already existing piston contraptions however I presume this is some lag management change?
Apparently it also fixes the sand/gravel duplication bug.
Doors being knocked by zombies show damage as cracks as in when you are destroying one.
Ice can be obtained by silk touch pick again.
Apparently, on Multiplayer you can hide your name plate while sneaking?? This will be interesting if true.
Finally: According to the Mojang site, New Biomes will generate on old maps on areas that haven't been generated yet!
There are actually quite a lot more changes but I just listed the ones that caught my eye as major changes!