For anyone interested in teaching introductory programming using a visual like interface, consider using Jeliot. As the help describes:
Jeliot is a program animation system intended for teaching introductory programming. Programs are animated automatically, requiring no modifications or annotations on the part of the instructor or student. Jeliot is written in Java for portability and animates programs that are written in Java.
The program usage is really simple. You load the code you want to visualize(it comes with already written examples you can pick of), click "Compile" and then "Run". As the program executes it displays the outcomes, assigning to variables, executing iterations etc.
For sure, I really had fun using it, and I would recommend to anyone that wants to teach introductory programming to use it. I hope to have some time to translate it to Greek language.
Check the web site for more details (you can easily start the program with Java Web Start)