Alternative to popular search engines that tags sites using "human beings and their judgement" to maintain quality but it is mostly intended to be spam free. Search a favorite topic and see what you think.
www.kidsreads.com This is a terrific site that provides high interest information about authors and children's books as well as reviews. The content is interesting to children as well as adults.
www.mymcpl.org/books-movies-music/juvenile-series This site maintained by the Mid-Continent Public Library contains a highly useful list of series and sequels for children's books that is searchable by subject, author, series title, and book title. This is the best source I have found for locating the sequence of series books for students.