this new update, Worked on mostly by Dinnerbone (a mojang worker). The update is 12w34a, it adds:

Flower pots to put flowers in.
Frames to Present Maps and items on the wall.
Added Walls.
New crops, Carrots and potatoes (there are Golden carrots too)
Mobs can now go into the nether through a portal
Added arrow-sensitive Buttons
Invisibility Potion, makes you invisible (Fun for multiplayer)
You can color Leather armor in crafting with dyes.
Bug fixes and New debugger options.
AND Maybe they might add Different Dog collars.

THERES SO MUCH MORE! thx for you time

DOWNLOAD HERE: http://assets.minecraft.net/12w34a/minecraft.jar