One Laptop Per Child (OLPC)
Also know as $100 laptop
The OLPC program was begun by MIT Media Lab veteran Nicholas Negroponte, with the goal of mass-producing low-cost, high performance laptops for children in developing nations.
Hardware is extensively described in the One Laptop per Child Wiki's hardware page.
Shipped software and ongoing official projects are described in the One Laptop per Child Wiki's software page.
The default operating system is Linux (Fedora 7), with a GUI called 'Sugar' which was created specifically for the project and which significantly breaks with conventional desktop models of user interface. Sugar, along with most official applications, is written in the Python computer language.
a project using the OLPC in NYC schools: http://olpcnyc.wordpress.com/