It is the 30th Anniversary of Banned Books Week—an annual event launched by the American Library Association’s Office of Intellectual Freedom to “promote awareness of challenges to library materials and celebrate[s] freedom of speech.”
The Banned Books Week Website includes a variety of information, including top ten lists of challenged books from the past decade. The 2011 list includes the legal classic To Kill a Mockingbird, by Harper Lee.
Federal Courts have struck down a variety of efforts to ban access to books. A list of some of these cases is available on the ALA website here.