JRuby Turtle Graphics
Tuga Turtle is a simple turtle graphics programming system I designed for my son. It uses the Ruby programming language which can be expressed in simple forms. On the plus side, Ruby is also a language used professionally for web programming and in many other fashions.
Here's a review of Tuga Turtle.
Here's an example of a simple program that draws a green square:
color green 4.times do turn right walk 500 end
Run Tuga Turtle here (about 1.5 MB total).
Accept the certificate in order to run the application. (You usually implicitly give the same trust to any other app you download.) It also requires Java 5 or higher to be installed your computer.
For more examples and ideas, click the "Programs..." button and then the "Examples" tab.
Tuga Turtle is free for home, school, or even commercial use (if you can find one).