"Sugar, the user interface for 'One Laptop per Child' is called (by Business Week) the "first complete rethinking of the computer user interface" since Apple's Mac appeared in 1984."
Called Sugar, the interface uses a highly abstracted spatial navigation metaphor, an extension of the familiar desktop metaphor, for easy, intuitive navigation that makes the most of the laptop's networking capabilities. Children can move through four levels of view—Home, Friends, Neighborhood, and Activity—and connect with others in the network "mesh" formed by users.
While traditional computer interfaces are modeled on the desktop metaphor, Sugar places the individual user at the center of the interface, which is icon-based and has four levels of view: Home, Friends, Neighborhood, and Activity. Users can move outward from the Home view, where they can set preferences like color, to the Friends view, where they can chat with their friends, to the larger Neighborhood view, where they can locate other users and gather around an activity. The Activity view looks inward: children, alone or together, can focus on a project at hand. In each view, a toolbar-like frame is available that organizes navigation, people, activities and files around the four sides of the view.
Users can actually try [Sugar] out
on their own computers if they'd like! The OLPC developers have
released VMs for a variety of F/OSS, free and commercial
virtualisation apps at their wiki.