Forbidden Library is a nice web site for people interested in banned and challenged books. The about page states:
The books listed on my site were all challenged on some grounds by groups who wished to impose restrictions on them. Some were removed from reading lists, some were removed from school or public libraries, some were burned in bonfires. I do not claim that all of the books in my list are for the same age group, nor do I believe they are all equally suitable for academic reading lists. I merely report documented challenges to books, and in some cases poke fun at the rationale used by those who object to the works mentioned.