Update 54 - This went live December 9. Conspiracies in Qeynos, Lucan missing, and Freeport goes boom. Also, like 200 bug fixes. West Freeport is a disater area, and it's awesome. This event will be ongoing until Update 55 in February (Halas!).
Moonlight Enchantments - These happen in 5 zones on the 20th of every month. I was so busy with college that I missed a few, but I'm catching up now. There are some really beautiful plant and crystal items as rewards. I bought a 5-room house in Maj'dul with Celestorm, and I'm using items from this monthly event to make it into an indoor forest.
Frostfell 2009 - This event is ingame right now and will end January 7. A lot of this is repeated content, but there's a heroic Icy Keep, and a new clockwork-related instance. I love my mini clockwork T-rex pet.
City Festivals - These will be out around January 8. From what I've read about this on the Test forums, there's some pretty nice appearance items and house items as rewards.
Sentinel's Fate - This expansion will be released in February of 2010. I've already spotted some familiar places and symbols in the screenshots. Long time no see, Kerra Isle!