Alice

Object theory created a paradigm shift in programming and since early 1990s it has been the mainstream programming technique. Alice is a free Program Visualization Tool from Carnegie Mellon University to help young students learn some of the main concepts of OOP like class, object, method, inheritance, encapsulation, abstraction and polymorphism. It is a very visual, 3D interactive animation environment and makes learning OO programming as simple as building Lego. Simple, effective, fun and great if you want to introduce your kid to programming.