A few hours ago notch revealed a few things that are going to be in 1.8.
NPC villages
Randomly generated dungeons
New biome code
Fully working Creative Mode (and individual admins can enter Creative Mode on a Survival Mode server if they choose)
Critical hits
Sprinting
More farming options
http://notch.tumblr.com/ for some more info.

I heard Notch was adding hunger as a part of it too?  Maybe I was misinformed, but...

I got my information from the Minecraft Forum's news, where they posted new features from players playing 1.8 from the PAX event somewhere.
So what I wrote is 100% true unless Mojang plans to change it.

The combat, the farming, the exploring, and the trading (possibly).  I'm excited for it all really.

Edit: Creative is going to be awesome as well.  Just forgot to mention.

Some things you need to know about this update:

No use for skillpoints (will come 1.9)
Villagers come 1.9
Bosses will come in 1.9
Some more biome codes and maybe a new biome  will come in 1.9
Running (also known as sprinting) will boost your jump from 2 blocks to 4
Melons is good  for filling your HungerBar 8 times ( i dont know the value)
Pumpkins used as mask so you don't get attacked by the enderman? (not sure)
Blue spiders can posion you
Hungerbar
Peacefull: you regen faster then the hunger kills you
Easy: hunger kills you for 5 hearts
Normal: hunger kills you for 9,5 hearts
Hard: hunger kills you

thats all you need to know :p
I can't wait for the update

Only 3 more days to go!

Good news Notch just tweet that 1.8 is uploaded!
 Notch: We just uploaded Minecraft 1.8, but minecraft.net isn't up right now because of web ops stuff.
So servers will be update soon as buckit comes
(Mesage for  EvilPoptart: Will you do minecraft video's now? )

Well I have been playing with this for about 2 hours now.. and I did fear this was extremely rushed by the surprise of them leaking 1.8 early. I now see why and for good reason and has been confirmed. Major game breaking bugs are in 1.8. Some of them which are not complete game breaking for me at the moment because of my computer, but others have not been so lucky.

I am very annoyed that F6 and F7 doesn't work for time advance, my character skin always flashes black and different colors have to hide it to prevent me from having a seizure, and a new memory leak crashes the game depending on if it likes your computer or not. Bah I only wanted creative mod to work right now which it does so that will not prevent me from working on things in there. I wish the flying wasn't so jerky, but then again I am trying to fly in water which is my fault. The fact I will be forced to work in the dark when night comes while in creative mod will be my biggest obstacle.

For reference purposes and this is for miles Id suggest not updating the SMP server because 1.7 maps are having issues converting and will corrupt the data file. *Afterthought* Take a gander at the 1.8 discussion on the forums for everybody complaining but im at least trying to at least pull some information from it for bugs minus the stupid people. 

http://www.minecraftwiki.net/wiki/Known_bugs/Version_1.8