Mojang (makers of Minecraft) released a Minecraft snapshot a few days ago, and it was full of nice goodies! A Minecraft snapshot is like a development version of Minecraft; you can play it by downloading it with your Minecraft launcher. Each snapshot will give you a hint to what will be in Minecraft 1.8. The biggest features so far for Minecraft 1.8:
Spectator mode: Lets you 'noclip' (go through blocks) and fly, but you don't get to see your inventory and no one can see you. Arrows pass through you, and monsters will not run after you, and you cannot push them. However, if you left click a creature, you can spectate them! Some mobs have certain visions. An enderman's vision is all white and inverted, and a spider's vision is like a bunch of eyes. A creeper's vision is green. You cannot control where they go, however. You can also spectate through the eyes of players!
New Skin Format: You know how you can have an extra layer called a 'hat' for your head? Well, now you can have that for your body! You can also remove outer layers, so you can basically have to skins at once!
New blocks: There are some new blocks, like the slime block which, when you fall on it, will take away fall damage and throw you into the air. Then there are some 'random' blocks like granite, and polished granite.