Dynasties & Demagogues is an excellent resource, as Crothian said; it includes a really great adventure (needs to be tweaked for AGOT, however, due to magic issues).
A free "official" adventure is supposed to come with the DLE of AGOT, isn't it?
Doubtless people will be posting their campaign/adventure ideas for AGOT over on the GoO forums, as Maester Luwin pointed out. Too bad they switched forums and lost all their data; there was a lot of useful ideas and stuff posted prior to the crash.