The 1.9 pre-release is out right now, download it at minecraftforum.net! Notch has also said that the 1.10 release will be coming soon, with even more Adventure-related updates. As we are going into the new update, the previous 1.8 section is now closed, and all 1.9-related discusson can be discussed here. Enjoy!
 
Server hosts can update their servers at minecraftforum.net.
 
1.9 includes:
 
•New mobs

•Villager

•Magma Cube

•Snow Golem

•Mooshroom

•Blaze

•New blocks

•Netherrack Bricks

•Netherrack Stairs

•Netherrack Fence

•Lily Pad

•New items

•Blaze Rod

•Ghast Tear

•Nether Wart

•Gold Nugget

•New generated structures

•Nether Ruins

•New Bugs

•Biome tinting is too harsh between regular water and swamp water, rather than blending.

•Can no longer jump repeatedly by holding a key

•Snow golems do not take fall damage

Wow minecraft is rapidly evolveing. This is awesome.

Notch recently commented on the perception of Endermen as they currently exist, saying "they're annoying, and because I nerfed them and made them too easy. I shall fix this." Any number of changes could be made to the Endermen to make them more difficult - more health, higher damage, more aggressive behavior - time will ultimately reveal any changes made to them.
 
Endermen have been a popular topic since their introduction in the 1.8 update, starring in numerous videos that run the spectrum from hilarious to terrifying. They have certainly set themselves up to be as well known (if not more well known) than Minecraft's ever-popular Creeper. What changes await this elusive monster? We will find out soon!

ALSO!

Jeb has provided us with the last Pre-Release version of 1.9 - get it here! Remember, this cannot be obtained via the launcher, and must be installed manually. Don't forget to report any bugs you find here, so they can be properly documented and fixed!
 
Server hosters can get the new SMP jar here.
 
Note: "There's a hardcore tooltip remaining in the world options menu. Please ignore it, hardcore is a game mode, not world option."
 
Notch also noted that there will be at least two more major additions to the game, followed by a code freeze (restricted code changes) prior to the official launch of Minecraft in November. Very exciting changes - keep an eye out for updates right here!
 
In addition to the wiki, you can check out (and talk about) the newly-discovered changes right here!

LAST BUT NOT LEAST!

Jeb has been discussing potions quite a bit lately - it seemed in the early stages of planning that potions would be brewed using a cauldron. However, recent comments strongly suggest that the cauldron is being replaced with a brewing stand (seen above).

In addition - Notch strongly hinted at an upcoming enchantment system, complete with an enchanting table or similar object (seen below). While he did confirm that it would cost Experience Points, have a 3-tier system and be "totally random", any other information on the topic has been somewhat cryptic.
 
With all the recent monster, item and biome additions to the game, one thing is for certain - 1.9 will be a feature-packed release!

i don't know what just happened

Potions have already been confirmed for a future release - but how many can there be? Jeb had this to say about it:

"In the prerelease, there are 161 brewable unique potions. Unless we change it, there will be 2,653 with all ingredients added."

While the code for potions is already somewhat in place, there do not appear to be any plans to make them available until the 1.10 release. We do not know all 2,653 possible future combinations; however, we have compiled a brief list of some known potions and their effects. Take a look at minecraftwiki.net/brewing

LOL It has a humungus head.. Well compared to Its body.