Enderman
Silverfish
Cave Spiders

Stone Brick
Stone Brick Slabs
Stone Brick Stairs
Brick Slabs and Brick Stairs
Fence Gates
Glass Panes
Iron Bars
Melons

NPC Villages
Strongholds
Abandoned Mine Shafts
Ravines

Rivers flowing through/in between biomes.
Ocean Biomes, that are deeper and much more vast than before.
Mountain biome
Swamp
Snow in Taiga and Tundra biomes do not generate for technical reasons. They return in Beta 1.9. New ocean floor; random mix of sand, dirt, and clay.
Because of this, clay is much more common.

Hold-to-charge bows.
Critical hits.
Players can parry with a sword by holding Right Mouse
Hostile mobs perform attack animations.
Mobs killed by players drop tiny flashing Experience Orbs that add to your experience bar.

There is now a food meter.
Food no longer heals directly but indirectly: if the food meter is above 90%, heals about every 5 seconds.
All food (except Mushroom Stew) are now stackable.
Food takes 1.6 seconds to consume, accompanied with an animation.
5 new food items.
Melon Slices.
Raw Chicken.
Raw Beef.
Cooked Chicken.
Steak, which has Cooked Porkchop's old texture. Cooked Porkchops' new texture is a tan shade of the same sprite.
Eating any raw food or Rotten Flesh has a chance to give the player food poisoning which makes the Hunger bar decrease three times as fast.

Mob changes
Passive mobs will randomly flee if attacked by the player or other mobs (such as Wolves).
Zombies drop Rotten Flesh instead of Feathers.
The snout on pigs now protrude from their head.
Skeletons now hold full-size bows.
Player-to-mob damage decreased by half a heart.
Arrows that hit a mob visually "stick" into the mob rather than just disappear.
Skeleton arrows originate from about their eyes to the bow, instead of above the head.
Animals no longer despawn which makes it possible to capture them.
Shears can now collect Tall Grass and the new Vine

Day/night cycles no longer require chunk updates and is a smooth transition
The lighting on a block is given a tint based on the most prominent source of light
Redish from Non-sunlight light sources
Blue from Moonlight
Total darkness keeps the same black tint
Sunlight gives the same white tint
Non-sky based light now gives a very subtle 'flicker'.
New Mojang logo splash screen
Main Menu/Options changes
The Main Menu's background is now an animated scene.
The version tag is now displayed on the bottom-left rather than the top-left
New sliders for Field of View and Brightness
4 new entries in control list
"Attack", "Use Item", and "Pick Block" can now be remapped