From the Events Calendar for December:
|Darkmoon Faire (Elwynn)||Mon December 4 - Sun December 10|
|Feast of Winterveil||Fri December 15 - Fri December 29|
|New Year's Eve||Sun December 31|
|Call to Arms: Warsong Gulch!||December 1 - December 4|
|Call to Arms: Arathi Basin!||December 8 - December 11|
|Call to Arms: Alterac Valley!||December 22 - December 25|
|Call to Arms: Warsong Gulch!||December 29 - December 31|
During a Call to Arms, emmissaries from that Battleground will be found in the major cities, and honor/faction rewards for performing objectives in that battleground are increased.
I can't wait to dive into the Feast of Winterveil. It's one of the best times in the game for me.