Scratch — Programming for kids

Scratch website.

Description from their site:

Scratch is a new programming language that makes it easy to create your own interactive stories, animations, games, music, and art — and share your creations on the web.

Scratch is designed to help young people (ages 8 and up) develop 21st century learning skills. As they create Scratch projects, young people learn important mathematical and computational ideas, while also gaining a deeper understanding of the process of design.

Scratch is available free of charge, go to Download.
Currently available for Mac OSX and Windows ( system requirements)