Snapshot 16w 20a
* Note - these changes and features are not 100% finalised *

NEW ITEMS:

Bone Block
Magma Block
Red Nether Brick
Nether Wart Block
Polar Bear (mob)
Stray (mob)
Husk (mob)

CHANGES:

New spawn eggs for: mule; donkey; skeletal horse; zombie horse; cat
Structure blocks for map makers, a new technical block for them
New fossil- like feature
Auto- jump, configurable in the settings
Endermen are invading the other dimensions
Mineshafts in the mesa are changed
New blocks in the nether
Changes to coordinates
New mob in hot and dry areas
New mob in the cold biomes

Snapshot 16w 21a

CHANGES:

New function to structure blocks
Bug fixes
Fishing items drags them towards you
Whilst in a boat you can get mobs into the boat (shooting mobs can shoot from the boat)

BUGS:

The lava looks like blood
Mobs don't appear to avoid the magma block

1.10 Pre Release 1

Mainly bug fixes in preparation for the official release of 1.10.

1.10 Pre Release 2

More bugs have been fixed and addressed, end stone brick is craftable again and missing mob sounds have been added into the game.

Bugs:

Polar bear spawn egg temporarily unavailable
Spawn eggs for husk, stray, elder guardian, skeleton and zombie horse

1.10 Release
(Directly pasted from Mojang website)

What comes after 9? Well surprise, surprise: we’ve updated Minecraft to version 1.10! Get it hot off the stove in the Minecraft launcher.

The update contains changes for both the coldest and hottest areas of the Minecraft world. Polar bears roam the frozen plains, and a stronger kind of zombie may approach you in the deserts. There are also other additions you may find pleasant.

For instance, the update includes the second “technical block” after Command Blocks: the Structure Block. This block allows map makers to store templates of structures and place them dynamically with the help of Redstone trickery. Since it’s a technical block, you will not find it in the game menus, and is restricted to players who are admins in creative mode.

Here is a list of all the changes:

• Many bug fixes
  
• Added Polar Bear
  
• Added Husk and Stray
  
• An auto-jump option
  
• Improvements to some commands
  
• Structure blocks for custom maps
  
• Underground fossils made from bone blocks
  
• Added Magma Block
  
• Added Nether Wart Block and Red Nether Bricks
  
• Some huge mushrooms can be even larger
  
• A rare chance to find lonely trees in plains
  
• Find abandoned mineshafts filled with gold in mesa biomes
  
• Villages generate better paths between the buildings
  
• More variations of villages, based on the biomes they are built in
  
• Endermen have been spotted in the Nether
  
• Removed Herobrine