UPDATE:
The Snapshot has now been updated to 14w30b, to fix two major issues (crashes, and holes in the world when viewed from certain angles).
Get ready for an awesome Snapshot! New methods to get mob heads, major optimizations, banners, and more! Read below for more info!
Today is special for another reason as well - it is Mojang developer Dinnerbone's birthday! I'm not saying you should tweet "happy birthday" to him, but if you did, it would make his day!
Read on for changes, bugfixes, and all the Snapshot goodies!
CHANGELOG:
- Added Banners! How do they work?
- Made Creeper, Skeleton and Zombie Heads available in survival. How? Don’t ask me!
- Major optimizations to client rendering. It’s magical!
- Lots of fun bugs fixed. Lighting should behave a little nicer now!
- Crafting cuddles now requires one extra hug in the recipe.
BUGFIXES GALORE:
- Bug MC-7508 – lighting error due to Chunk.heightMap ignoring block at the top level of an ExtendedBlockStorage instance (off by 1 error)
- Bug MC-32514 – The well in a desert village is made out of the wrong material/cobblestone
- Bug MC-58790 – Sign with give / replaceitem doesn't update player inventory
- Bug MC-60301 – Broken resource packs: Game Crashes when i try to load 14w27a/b
- Bug MC-60552 – Flower pots with metadata placed in 1.7 will not render in 1.8 snapshots / metadata not removed
- Bug MC-62127 – Turning off VSync crashes the game
- Bug MC-62138 – "#PLAYER" Appears on Sidebar
- Bug MC-62170 – Carpet has incorrect height?
- Bug MC-62180 – /testfor @p doesn't consider x,y,z anymore
- Bug MC-62223 – Crash in Video Settings menue
- Bug MC-62240 – command selector parameters dx dy dz don't work
- Bug MC-62267 – Game crashes when trying to enable VSync
- Bug MC-62342 – Slabs can not be placed in adventure mode with tag CanPlaceOn.
- Bug MC-62349 – Hopper: java.lang.NullPointerException: Saving entity NBT
- Bug MC-62379 – Spawners (Dungeons, Strongholds, etc…) can spawn mobs outside of worldborder
- Bug MC-62419 – Hopper: java.lang.IllegalArgumentException: Cannot get property bcy{name=half, clazz=class ats, values=upper, lower} as it does not exist in bch{block=minec
- Bug MC-62493 – "/worldborder get" can display invalid size using "/worldborder add"
- Bug MC-62499 – /replaceitem block has incorrect syntax
- Bug MC-62504 – /kill adds 214748364 / 0xCCCCCCC to "Damage Taken" statistics
- Bug MC-62507 – Overlapping Dungeons Don't Spawn Correctly
- Bug MC-62655 – Cubic player selector always finds player if there are more than 31 Entities around
- Bug MC-62736 – ReplaceItem command not updated when the command was executed with a sign
- Bug MC-62789 – Chunks containing paintings may be wiped and regenerated upon load
Please report any and all bugs you find in Minecraft to bugs.mojang.com. If nobody reports a bug, it will be the worst birthday ever! 
To get snapshots, open your launcher and press the “New Profile” button. Call it “snapshots” and check the box saying “Enable experimental development snapshots” and save. To switch to the normal version, you can select it in the dropdown at the bottom left corner of the launcher. Back up your world first or run the game on in a different folder (See the “new profile” dialog).
Snapshots can corrupt your world, please backup and/or run them in a different folder from your main worlds.
CROSS-PLATFORM SERVER JAR:
https://s3.amazonaws.com/Minecraft.Download/versions/14w30a/minecraft_server.14w30a.jar
REPORT BUGS: