The title of the Doctor Who 50th Anniversary Special has been revealed, it is:
The Day of the Doctor
Check out the new promo posters HERE. The story, starring David Tennant and Matt Smith (amongst others) and written by current showrunner Steven Moffat, has a running time of 75 minutes and will air worldwide on November 23, 2013. The DVD is released on Dec 2, pre-order HERE.
For more info, visit the Blogtor Who guide to The Day of the Doctor HERE.