Freedom of Speech and Press: Exceptions to the First Amendment [Updated September 9, 2008] [open pdf - 236KB]
"This report provides an overview of the major exceptions to the First Amendment -- of the ways that the Supreme Court has interpreted the guarantee of freedom of speech and press to provide no protection or only limited protection for some types of speech. For example, the Court has decided that the First Amendment provides no protection to obscenity, child pornography, or speech that constitutes 'advocacy of the use of force or of law violation ... where such advocacy is directed to inciting or producing imminent lawless action and is likely to incite or produce such action.'"
CRS Report for Congress, 95-815
U.S. Dept. of State, Foreign Press Centers: http://fpc.state.gov/