At today's Children In Need Telethon they debuted a special preview trailer for the Doctor Who Christmas Special.
In addition, they revealed the title for the episode to be "The Doctor, The Widow and the Wardrobe."
Matt Smith also donated the Doctor Who attire he wears for episodes to be auctioned off for the charity.
Update: Here's the link for the Matt Smith outfit and signed script up at EBay.
Update #2: Now in HD.
Check it out: