Array Animation Language
A small, strongly-typed, imperative language designed for visualizing algorithms on array data structures.
Try it out here.
Info
An AAL program is compiled down to a sort of bytecode called AIS, which is then interpreted by an interactive JavaScript animation runtime built on HTML5 canvas.
There are many existing resources for visualizing sorting algorithms, but AAL can be used to easily experiment with new algorithms and interactively step through their execution in a visual environment. It's also useful for illustrating the call stack (it even grows downward!).