When the PC era began in the early 1980s, you'd be lucky to find a computer for under $3,000. Today, you can buy a notebook that's hundreds of times more powerful than the original IBM PC for well under $400, but for many people around the world, even that is too much. A new generation of low-cost tablets, USB-sized computers and miniature motherboards can put an entire world of computing power in the palm of your hand for as little as $25.