I've been keeping an eye on the OLPC (One Laptop Per Child) project for a while now, partly because I love the humanistic idea of utilising technology to drive improvements in education in developing countries, and also partly because of the interesting technology in use.
Read the website for details, but as an overview; the computer has no hard disk, runs a custom, slimmed-down version of a GNU/Linux O/S and uses a low-powered CPU.
Now, it would have been easy to make this a basic, low-end computer in the mould of what we are used to. However, they haven't; the thing has a webcam, sound and wireless networking and automatically creates "mesh" peer-to-peer networks with other nearby OLPC devices. It also promises a fairly radical UI (called "Sugar") that uses the mesh to interact with other users nearby in the context of social features and applications.
There's an article about the O/S here and a couple of great videos of the UI and social features in action here and here.