Final answer:
The First Amendment does not protect obscenity, libel and slander, or certain forms of symbolic speech such as cross burnings that violate other laws.
Step-by-step explanation:
The First Amendment of the U.S. Constitution does not protect the following categories of speech: obscenity, libel and slander, and certain forms of symbolic speech. Notably, political speech and commercial speech are generally protected, although the latter to a lesser degree.
Obscenity is not protected because it lacks serious literary, artistic, political, or scientific value. Libel and slander, which are forms of defamation, are not protected, permitting individuals who have been falsely accused to seek damages. Expressions such as cross burnings may also not be protected, especially when other laws are violated in the process.