TFormers.com has posted a possible teaser poster for Transformers: The Dark of the Moon that "Bru No" spotted at a hotel conference room. It is hard to tell if it is the real deal but includes a good look at the head of Shockwave as floats behind the image of the moon emblazed with the Decepticon logo and the tagline "Be Afraid of the Dark."
Update: Bumping up this post from 10/27/10 as to probably the surprise of no-one, the poster is a fake. Michael Bay did another one of his random drive-by on his official forums, posting, "Total fake poster. The story logline is also a misdirect." Thanks to NHLfan for the heads-up.