Here you will find all the information on the latest snapshots. Don't hesitate to tell me if I get something wrong!

Snapshot 13w19a [Key Changes]
-Added hardened clay
-Enabled access to donkey's inventories
-Mobs spawn as groups
-New textures for charcoal, coal blocks and Lapis Lazuli
-Bug Fixes

http://s3.amazonaws.com/Minecraft.Download/launcher/MinecraftDev.exe
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Snapshot there. Stay put for more feeds