Patch 3.3.0 is currently on the test realm (AKA the "PTR") and its release notes can be read at WoWWiki:

http://www.wowwiki.com/Patch_3.3.0

Be sure to check out the undocumented changes link in the box at the right on that page to see things not in the official notes.

Some notable changes:

• Two new 5-man dungeons are added.
• Low-level spells are being adjusted to use less mana (important for alts).
• A new quest management feature is planned but not yet available on the PTR.
• A new weekly raid quest that awards an [Emblem of Frost] is added, requiring that one kill mobs from different raid dungeons each week.
• The loot greed/need dialog now includes a "disenchant" option.
• Enhancements are being made to the LFG tool, and 3 achievements are added to encourage its use.