A (?) denotes version's info here is guess-work, possibly incorrect. Known bugs in the latest stable version are listed here, and in the latest development version here.
Version
Date of Addition
Additions Summary
1.2.2
March 1, 2012
"Uploaded Minecraft 1.2.2 because birches and pine trees were missing..."
Big trees, swamp trees and giant mushrooms are back too.
Added 3 new blocks textures, that aren't yet used in the game (1 is accessable in creative, it looks like stone brick)
You can place Slabs and Stairs upside-down by placing them on the ceiling
Many other minor tweaks and fixes
Placing blocks on Wild Grass will replace them
Lava now has a faint rumbling sound effect, and large particles that hop out of the lava produce a popping noise.
Very rare Desert Wells can be found in Desert biomes.
F3 has some changes and additions:
b: Shows what biome you are in
lc:
bl: Block brightness
sl: Sky brightness
rl: Raw brightness
It doesn't show the seed in SMP (due to popular demand) anymore
Bug Fixes :
Doors have been updated so that double-doors work better with redstone
Cave Noise works in Multiplayer
Mob spawners are showing the right mob in SMP (instead of a pig)
Bugs :
Very rare big trees in Forest, birches, pines in Taiga, swamp trees in Swamps, giant mushrooms in Mushroom Biomes
99% of the big trees are replaced by small trees, so no big trees in biomes like Mountains that could generate rare big trees
Snow doesn't appear on maps
F3 is taking more resources than before, making the game unplayable on old computers.
The biome "FrozenRiver" doesn't have a spacebar like other biomes (e.g. "Ice Mountains")
Maps in creative don't show anything at all
1.1
January 12, 2012
Bows are now enchantable, with four new enchantments specific to bows: Power, Punch, Infinity, and Flame.
Arrows which are on fire now set entities they hit on fire.
Golden Apple recipe changed to use gold nuggets instead of gold blocks.
Golden Apples now restore rather than and cause regeneration for 5 seconds rather than 30.
56 new language translations, including fictional ones such as Pirate, Klingon, and Quenya.
Infrastructure for improved mob AI added, allowing for more complicated behavior than before. These behaviors themselves have not been implemented yet.
Slightly smoothed color transitions between biomes.
Swamp land and water colors now smoothly transition to other biomes.
In SMP servers, non-ops are kicked if they spam in chat too much (Ops are not notified of the kick, they must assume that the player was auto-kicked)
The distance that Wheat attracts friendly mobs has increased from 2-3 blocks to 8-9 blocks.
All Music discs except for "11" can be dropped from creepers killed by skeletons.
Bug fixes:
Fixed "Sniper Duel" achievement not working.
Fixed Powered Rail Non-Depowering Bug
Fixed Powered Rail Failure-to-Update on Placement Bug
Bugs:
Major crash bug in the loading screen for some users
Possible to fall through a block of Farmland, Soul Sand or Glass when walking over its edge.
Open fence gates will close randomly or if they receive a block update.
Note blocks don't make a sound when hit in SMP.
In the creative mode block screen, if you click on a block that has the same ID but not the same damage value, the block you click with will still gain blocks.[Cr]
1.0.1
November 24, 2011
This was a server-only update, 1.0.0 remained the current client version.
On death, a proper score is given based on how many experience orbs the player has collected.
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.
Ender Pearls have a unique ability. 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.
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.
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.
The "/give" command can now set the damage value of the wanted item : /give username itemID quantity damage (For example: "/give player 35 12 1" to give 12 orange wool.)
"The End" (unofficially called "The Ender", or "Enderlands"), which replaces the previously announced Sky Dimension.
End Portals take the player from the Overworld to The End. To go back to the Overworld, one must defeat the Enderdragon and jump through the portal that appears.
The true sounds of Endermen and Silverfish. ( Enderman and Silverfish have new sounds instead of just Zombie sounds for Enderman and Spider sounds for Silverfish).
New sounds for the Skeletons' walk to make them sound more skeleton-y.
Bow models now appear in third-person larger and in 3D.
Bows no longer have an infinite number of uses. (385 shots before breaking)
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.
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.
Oftentimes when trying to connect to an SMP server, the error "The server responded with an invalid server key" will show instead. This is followed by an "End of Stream" error which appears whenever a connection attempt to the server is made for up to 60 seconds after the initial attempt.