This is just a collection of data that I've found while playing the Minecraft 1.8 Pre-Release. I will add more if and when I find them.
1.) Using a crafting table in Creative Mode displays the crafting GUI as well as your inventory.
2.) In Creative Mode, you can still throw away items, and eventually you'll stop being able to pick them up. (Due to you having an inventory, and this getting full)
3.) In Creative Mode, items are only infinite when you place them. Food items, and arrows aren't infinite.
New Crafting Recipes
4 Stone -> Stone Bricks
3 Stone Bricks -> Stone Brick Slab
6 Stone Bricks -> Stone Brick Stairs
3 Bricks -> Bricks Slab
6 Bricks -> Brick Stairs
6 Glass -> Glass Pane
6 Iron Ingots -> Iron Bars
4 Sticks + 2 Wood -> Fence Gate
This is what Endermen drop. It's called an "Ender Pearl." At the time of this writing, they don't do anything.
Cows will drop this:
The left is "Raw Beef," and when cooked will make the right, which is "Steak."
Chickens now drop this:
The left is "Raw Chicken," and when cooked will make "Cooked Chicken."
On top of that, there's also a new texture for cooked porkchop: