Berries at Blueberry Hill
Multiply your blueberries and defeat the computer in this strategic online game. It's rather like Othello, and would be a good introduction to chess for younger children.
The Grey Labyrinth
An award winning site of mathematical puzzles both solved and unsolved! A forum is also provided where you can discuss the problems with other visitors.
Interactive Mathematics Miscellany and Puzzles
Great site with a number of interactive puzzles. Many of these are challenging although secondary students should be able to approach these given some assistance, ideal for developing understanding.
Logic Mazes
An enthralling collection of interactive mazes, at least one of which was too much for the editor of this site. Theseus and the Minotaur is particularly compelling. 
clipped from: education.guardian.co.uk