There are no books officially banned in the United States, though specific titles are frequently challenged in school curriculums and public libraries. In the early '90s, the American Library Association recorded over 6,000 challenges.

And while the First Amendment protects printed materials, it's safe to assume the American government wouldn't appreciate a dirty bomb instruction manual. Certain types of sensitive information are restricted by law.

Banned Books Online offers a brief but fascinating overview of banned books in this country. Some perennial banned favorites include "Of Mice and Men" and "Huckleberry Finn." Lately, the "Harry Potter" series has generated controversy due to its use of magic and witchcraft.

Every year, the American Library Association sponsors Banned Books Week, an effort to raise awareness of censorship issues. They also offer a list of the most frequently challenged books of 2003.