The folks at Mojang have put together the latest snapshot or development build of Minecraft which adds quite a bit of changes to the existing game, bringing it up to version 13w24a.
The new version of Minecraft builds upon the new Resource Pack system, which has finally gone live. According to the developers, it's a "huge step forward" for the future plugin API and will replace texture packs in their current iteration.
Existing texture packs will no longer be supported through the new Resource Pack system, but fortunately Mojang has released a tool to automatically convert them.
You can grab that tool here.
Other improvements to the game include fixes to achievements, bug fixes relating to mob spawning, and a host of animation issues.
Grab the update here.
