This is snapshot 12w41a. It is a snapshot for minecraft 1.4 wich comes with halloween.
In this snapshot there is a new block called an anvil! And afcourse some bug fixes.
What is new:
*Added a new Anvil block for repairing, merging & naming items
*Added an option for cape-owners to hide their capes ingame
*Effects given by the Beacon will be less intrusive on the screen
*Level-up sound now only plays every 5 levels
*More bugfixes & tweaks!

You find the download links over here: http://www.youtube.com/watch?v=0qmu61SIhO0&list=UUD650XOlWVNXhExckAIM_Mg&index=1&feature=plcp