You're probably familiar with Scratch, the introductory programming language that allows kids (and adults) to create interactive stories, games, and animations. Scratch doesn't require lines of code to write programs. Instead, you build programs by snapping together colored blocks. (My book, Maker Dad, has an introduction to Scratch that shows how to make retro-style video games).
Scratch is perfect for kids 8 and up. Recently, MIT Media Lab's Lifelong Kindergarten Lab announced the release of ScratchJr, an even simpler programming language for young children (ages 5-7) to create interactive stories and games. It's free and runs on iPads and Android tablets.
Mitchel Resnick, who runs MIT Media Lab's Lifelong Kindergarten Lab, and Marina Umaschi Bers, a professor in the Computer Science Department at Tufts University, have a new book out called, The Official ScratchJr Book: Help Your Kids Learn to Code. The publisher sent me a copy, and it looks like a great way for parents to learn about ScratchJr so they can get their kids up to speed and let them go off on their own. With full color screenshots on every page, it provides a thorough overview of everything ScratchJr is capable of doing.