because people seem to be confused
The American Library Association has a list of the "The 100 Most Frequently Challenged Books of 1990–2000," located here
. Yes, that says "challenged;" not all of them have necessarily been banned.
Explanations for many challenges/bans are located here
The ALA also has a page
containing a summary of "Challenges by Initiator, Institution, Type, and Year." It doesn't address any of the individual titles, but is good if you just want an overview of why/when/where/by whom books are challenged.
[And for any who don't know why this lemming is going around, Banned Books Week
is this coming week, Saturday to Saturday. My lemming-ness regarding this list is located here