It took some digging, but TPM Muckraker has discovered that the Pentagon has classified the monthly number of attacks in Iraq.
As Doonesbury once observed, this information is hardly "secret" to the people who are getting blown up over there. They're only a secret from us. Once upon a time US government propaganda and government secrecy were weapons directed toward the enemy. It's the peculiar genius of the Bush administration to target its own fellow citizens with them.
The Muckrakers are calling for suggestions: What other pieces of information has the Bush administration simply classified and hidden away rather than having to address the problem the information reflects? (Usually, it's a problem only insofar as it contradicts the Bush ideological party line on tax cuts, deregulation, privitization, or reproductive freedom.) Check out the list they've assembled so far, and prepare to be appalled.
I started keeping track of this trend in 2005, but soon got swamped, and a little depressed. You can read the examples I cataloged here, here, and here.