From Free Technology for Teachers - Database for Award-Winning Children's Literature. It offers a variety of search options including genre, gender of protagonist, age ranges from baby to 14+, historical period, publication date range, and language. Click the image for a better view of the search options.
From Joyce Valenza's NeverEndingSearch blog - SweetSearch for students. Every web site has been evaluated by their research experts. There is a nice collection of links organized by subject and level in the Web Links section.