They're unpredictable, those Mojang people. You turn your back for but a second and they start doing all sorts, surprising us with new features or new mobs or, this time, giving us the latest snapshot a day early.
You can grab it here and while there aren't any major changes this time around, it does make a few tweaks and iron out some troubling, game-crashing creases.
Most significantly, the new anvils are now a little cheaper to make, requiring only iron ingots for their base instead of the three iron blocks in the original crafting recipe, and you can now use wood, ingots or diamonds with them to repair your tools. The engineers among us will be interested to know that you can also lock Redstone repeaters by connecting another powered repeater on their left or right side. For a complete list of the minor glitches addressed in this snapshot, check out the Minecraft Wiki.
Oh, and if you're trying out a new snapshot for the first time, don't forget that we have a guide here to help you.