The last week in September is Banned Books Week. To mark the event, an interactive map has been created that shows requests for removal of books from public libraries and school libraries for the period 2007-2009. The map is created from cases reported to and documented by the American Library Association.
The image above is a screencap. The interactive map itself can be accessed at this link.
The ALA also has a listing of the top ten most frequently challenged books for 2008.