Interpreter for LOGO language
In javascript with SVG for graphics ( you need SVG plugin )

Interpreter is not complete, you can move turtle ( hier it's a frog of course ... ), create variables,  procedures. You can use recursivity. You can see classical examples of fractals ( as Von Koch's curve, Sierpinski's triangle ... ).
In Help you get a list of primitives interpreted and syntax used.

Try application starting with example ( PHP version ):
Von Koch's curve    Sierpinski's triangle     Many squares

Try application online (  version without PHP  ) 

Load in Zip file application without PHP and help file  ( 5 ko )
Load PHP version of application with help file and examples ( 5 ko )