Under the category of Challenge - the public library board in Topeka, KS, has voted to restrict 4 books on sex based on a challenge from the community:
From the International Herald Tribune
http://www.iht.com/articles/ap/2009/02/20/america/NA-US-Library-Sex-Books.php

Another news story on this event, with responses from the library community:
Library Peers Dismayed at Board's Decision
http://www.cjonline.com/stories/022109/kan_396302566.shtml

And on the Topeka ABC affiliate's web page, a local lawyer says that the ACLU may become involved. Check out the poll at the bottom of the page - it is currently ahead on "Yes, children must be protected from exposure to certain books" http://www.ktka.com/news/2009/feb/20/local_attorney_people_want_legal_action_against_li/