Minecraft is a game about placing blocks to build anything you can imagine. At night monsters come out, make sure to build a shelter before that happens. It also has music by C418! So far 23,633,8778 people have registered and 5,184,2845 people bought the game. More stats here.
ABCya.com is the leader in free educational kids computer games and activities for elementary students to learn on the web. All children's educational computer activities were created or approved by certified school teachers. All educational games are free and are modeled from primary grade lessons and enhanced to provide an interactive way for children to learn.
The BBC has excellent educational games, activities, and resources. The BBC Science Clips are a collection of science related activities and games for students who are 5 to 11 years old. Students can grow virtual plants, experiment with pushes and pulls, hearing and sound, forces and movement, electricity, rocks and soils, simple machines, light, solids and liquids, friction, habitats, life cycles, changing states of matter, reversible and irreversible changes, forces, and much more.
"Tony DeRose wanders between rows at New York's Museum of Mathematics. In a brightly-colored button-up T-shirt that may be Pixar standard issue, he doesn't look like the stereotype of a scientist. He greets throngs of squirrely, nerdy children and their handlers - parents and grandparents, math and science teachers - as well as their grown-up math nerd counterparts, who came alone or with their friends. One twentysomething has a credit for crowd animation on Cars 2; he's brought his mom. She wants to meet the pioneer whose work lets her son do what he does."