The Word of Notch has details on a new beta version 1.2 of Minecraft that's now available. The Minecraft Forums have more details and discussion of the new version (thanks Ant). The partial change list follows.

Minecraft Beta 1.2 is live. All servers need to be updated to 1.2.

New features:

• Note blocks (right click to tune, trigger to play)
• 15 wool dyes
• A new water dwelling mob
• New tree types
• Reeds magically turned into sugar canes. They still make paper.
• A bunch of new crafting recipes
• One secret useful block
• One secret pretty block
• Cake
• AND MOAR, probably. I forget!

Bugfixes:

• Paintings work in multiplayer
• Disconnecting while riding no longer keeps the player in the world
• A bunch more state is properly synched in multiplayer
• Fixed colors going weird on PowerPC
• Fixed a horrible chunk reload loop in singleplayer
• Fixed most lighting bugs in newly generated SMP maps
• Falling sand behaves better in SMP
• Fixed a few crash on load level bugs