HBO have revealed a very brief teaser for Game of Thrones. The teaser features brief glimpses of Sean Bean as Eddard Stark, Alfie Allen as Theon Greyjoy, Bronson Webb as Will and Richard Ridings as Gared, along with shots of the Dothraki wedding scene and the Stark expedition riding to Winterfell. Westeros.org has an excellent analysis of the trailer here.
HBO have also released a new official image, this one of Sean Bean as Eddard Stark, which can be downloaded in three sizes (1920x1280, 1280x720, 1024x576).
In addition, HBO have added a Game of Thrones-centric subsite and forum to their main website and confirmed that a veteran Dexter director, Brian Kirk, will be handling two episodes of the first season.
Thrones' first season starts shooting on 26 July and will air on HBO around April-May 2011. The BBC are reportedly involved in financing and will air the show in the UK, although a date has not been given as yet.