Mojang recently released Snapshot 13w19a, which can be downloaded from the official Mojang website here for Mac/OSX, Windows, Linux, and whatever other platforms you play Minecraft on.
This snapshot comes with the usual mix of bug changes and minor gameplay tweaks, including:
-Added new stained hardened clay
-New and improved textures for Lapis Lazuli, Coal Black, and Charcoal
-Players now have access to donkey and mule inventories by sneaking and interacting
-Mobs spawn as groups again
-Fixed bug that caused minecarts with furnaces to consume coal in creative mode
-Fixed bug that gave players a glitch bow after using a bow for the last time
-Fixed bug that caused coal blocks to not burn away
-Fixed bug that blurred menu background textures
Once again, to download that snapshot today for the server or client version of Minecraft, click here.