American Library Association
BookBrowser Contains book reviews and lists by genre.
BookMuse.com "Kids Corner" section includes book reviews and discussion guides for kids.
BookSpot.com Provides links to information on just about every aspect of reading and books.
Random House - reader resources Includes links to other publishing groups, which also have discussion guides.
ReadingGroupGuides.com Includes "hundreds" of discussion guides, including non-fiction, arranged by subject.
Reading Group Choices More advice on starting a reading group, as well as discussion guides.