Mojang is getting in a Halloween spirit with this week's snapshot, so let's get right to it! This week adds bug fixes to the Nether, that should bring an end to lag when entering the Nether. New sounds from C418 for placing blocks, walking, and mobs have been added this week. There are two new mobs this week, one of which is the new Bat, which spawns in dark caves (even in Peaceful) and starts flying when approached. The other new mob is the Witch that throws potions at the player, regenerates health, and does not spawn naturally (must be hacked in or use a creative egg). Get the full changelog at the source links below, and the download at Mojang's site link.Source: Minecraft Wiki, Mojang