The MIT Media Lab's Lifelong Kindergarten Group created the Scratch programming language that makes it easy to create your own interactive stories, animations, games, music, and art -- and share your creations on the web (description from their website). It is available as freeware for Mac OS X and Microsoft Windows. A version for Linux is currently being developed according to the note on the download page. You can learn more about working with Scratch on its Informational Page.