Read the changelog and get the snapshot here - http://www.mojang.com/2012/06/minecraft-snapshot-week-25/

• Added a menu with options for opening your single-player world
• The multi-player menu now scans for LAN servers (single-player worlds)
• Villagers will remove trade options after the option has been used 3-15 times
• Added wooden stairs for the remaining three wood types
• Corrected Ender Chest storage (no longer whiped on respawning)
• A lot of smaller changes and fixes