EToys is quite nice http://www.squeakland.org http://www.squeakland.org It's a Smalltalk environment extended with a drag-and-drop scripting system. All (liter

EToys is quite nice http://www.squeakland.org http://www.squeakland.org It's a Smalltalk environment extended with a drag-and-drop scripting system. All (literally, all) of the graphical objects can be used as turtles (they have a "pen", and methods for "forward", "left"/"right", etc.). The really nice part is that it's "turtles all the way down": the entire GUI (scripts, text, buttons, etc.) is made out of the same stuff as user-created objects; you can write scripts which tell other scripts how to move around; and write scripts to tell those scripts how to move around; and so on. It comes with a bunch of pre-built objects, including a musical keyboard, a paint program, etc. and there are projects like "physical etoys" for hooking in physical sensors and actuators, so you can make a physical turtle.