There are many great websites that you can try.

PBS Kids                                                         The KIDZ Page                                           Magic Tree House

Make Me Genius                                               Funbrain                                                   ABC Mouse

Starfall                                                            Storyline Online                                         switchzoo

The Magic School Bus                                       The Happiest Scientist                                seussville

Cool Math                                                        Cells Alive                                         

Highlights Kids                                                 Youngzine

ABCya                                                             Fuel the Brain

National Geographic Kids                                   e-Learning for Kids