This energetic site is new to me. It's all about books, and games based on books. There are sections where kids give their opinions. Some teachers get into it, too.
I read about it in the San Diego Union Tribune, under Surfing With Kids, by c. Barbara Feldman at email@example.com.
Featured on kidsreads.com is Harry Potter, with lots of games and quizzes.
She mentioned other sites: http://harrypotter.warnerbros.com, and mugglenet.com
If I had kids under 30, I would definitely use this site with them.