ASCEND is an interactive environment for modeling, debugging, and solving large systems of nonlinear algebraic or differential equations. Oriented towards chemical engineering applications, it includes a large Open Source thermodynamic properties database. The interactive design allows users to inspect and solve very difficult nonlinear systems. It includes plotting abilities and is scriptable using both Python and Tcl/Tk.
Alana is a highly responsive Turing Machine simulator with many examples, like (unary and binary) addition, subtraction and multiplication, "copy band content", string parsing examples, and divisibility and primality testing. The documentation contains an introduction to Turing Machines as well as some interesting theoretical information (halting problem, busy beaver, universal Turing Machines) and pointers to further literature.
AsciiArtWidget creates and handles a widget with bindings appropriate for easy creation of ascii art. Basically it is a text widget filled with spaces and newlines, and character inserts replace a space, and backspace/delete replace characters with spaces so that the right hand side of the image is always in the right spot. Includes a mouse drag painting binding, and block sleection/delete, as well as a data loading and squaring system.