At about the size of a wallet, and for a cost of only $35, the Raspberry Pi is quite a little computer. It's literally just a small, single motherboard with 256MB RAM, an SD card, ethernet and USB port that runs Linux and costs next to nothing.
At such a low cost, it's intended to be an intro computer for kids and schools. Running Linux, and without much memory, there isn't too much it can do compared to what most people are used to nowadays. But as far as some basic teaching, or teaching BASIC (a programming language,) it definitely suits a need. Demand has already surpassed expectations. Future versions are looking to bundle a wi-fi adaptor, keyboard, and SD reader. For now, the Raspberry Pi is only being sold online.