Capstone Kids: a fun place for kids to explore - characters, make stuff, play games, etc.
Epic! provides free access to thousands of popular, high-quality eBooks, videos and quizzes for K-5 classroom use.
PBSkids.org: loads of activities related to your favorite PBS Kids programming like Arthur, Reading Rainbow and Clifford.
KidsReads.com: A place for kids to find info about their favorite books, series and authors. See reviews of the newest titles, interviews with authors, special features on great books, as well as trivia games, word scrambles and contests.
MerriamWebster Visual Dictionary Online: The Visual Dictionary, filled with illustrations labeled with accurate terminology, is the ideal language:learning and vocabulary dictionary.
Merriam WebsterWord Central: Merriam:Webster's area for kids on the World Wide Web, hosts an online Student Dictionary, Student Thesaurus and much more.
Rhyme Zone: Rhyme Zone is an online rhyming dictionary.