There is a difference between books banned by government action (e.g., Ulysses or Tropic of Cancer) and books banned by a community or a library (e.g., Harry Potter, Huck Finn). Here's a list from the American Library Associations Intellectual Freedom Committee of the 10 most challenged (but not necessarily banned) books of 2007:

   1. And Tango Makes Three, by Justin Richardson/Peter Parnell
      Reasons: Anti-Ethnic, Sexism, Homosexuality, Anti-Family, Religious Viewpoint, Unsuited to Age Group
   2. The Chocolate War, by Robert Cormier
      Reasons: Sexually Explicit, Offensive Language, Violence
   3. Olive's Ocean, by Kevin Henkes
      Reasons: Sexually Explicit and Offensive Language
   4. The Golden Compass, by Philip Pullman
      Reasons: Religious Viewpoint
   5. The Adventures of Huckleberry Finn, by Mark Twain
      Reasons: Racism
   6. The Color Purple, by Alice Walker
      Reasons: Homosexuality, Sexually Explicit, Offensive Language,
   7. TTYL, by Lauren Myracle
      Reasons: Sexually Explicit, Offensive Language, Unsuited to Age Group
   8. I Know Why the Caged Bird Sings, by Maya Angelou
      Reasons: Sexually Explicit
   9. It's Perfectly Normal, by Robie Harris
      Reasons: Sex Education, Sexually Explicit
10. The Perks of Being A Wallflower, by Stephen Chbosky
      Reasons: Homosexuality, Sexually Explicit, Offensive Language, Unsuited to Age Group

Note, please, that some of these books have been around for a while....