Show Me "Shows you the cool, fun, scary, wild, crazy stuff from the UK's museums and galleries".
There are topics to pick from including Science and Technology, Art and Design, the natural world, dinosaurs etc., which each have games to play, stories to read, ideas for stuff to do at home and links to other websites on the topic.
Seems like a very educational site for children, including a parents and teachers sections, however not very colourful and don't think it would keep attention very long, if it gained their attention to begin with.
Would recommend to people purely for the educational factor.